The TandemHeart Drains the Left Atrium to Support the Failing Ventricle. Here Is How It Compares to Other Percutaneous Devices.

The Scene

The cardiologist in the cardiac ICU at Rush University Medical Center in Chicago is managing a 55-year-old man who has been in cardiogenic shock for 18 hours following his second myocardial infarction. His first MI was an inferior wall infarction six years ago; he recovered to an LVEF of 48%. This one has hit a proximal RCA with involvement of the right ventricle. The LVEF on echo is 20%. He has been on norepinephrine and vasopressin since admission. His cardiac output by thermodilution is 2.4 L/min.

The Impella CP has been considered but the access site on the right femoral artery is compromised from a prior cardiac catheterization that left an occlusive scar. The left femoral approach is available but the left iliac artery has heavy calcium and the interventional cardiologist is concerned about passing a 14-French sheath through it safely. The team is discussing TandemHeart as an alternative percutaneous support strategy.

The TandemHeart, manufactured by CardiacAssist (later acquired by LivaNova), takes a different anatomic approach than the Impella. Instead of pulling blood from the left ventricle, it drains from the left atrium via a transseptal cannula and pumps that blood back into the arterial circulation through a return cannula in the femoral artery or iliac artery. Left atrial unloading rather than left ventricular unloading. The distinction matters physiologically and anatomically.

What It Is

The TandemHeart is a percutaneous left atrial-to-femoral arterial ventricular assist device manufactured by CardiacAssist, Inc. (acquired by LivaNova in 2017). The system consists of:

1. The TandemHeart pump: a centrifugal-flow extracorporeal pump capable of generating flow up to 4.0 to 5.0 liters per minute at a rotational speed of approximately 7,500 rpm
2. The transseptal inflow cannula: a 21-French cannula placed through a percutaneous femoral venous approach, advanced via transseptal puncture from the right atrium into the left atrium, with the large-bore inlet positioned in the left atrium
3. The outflow cannula: a 15-17 French arterial cannula placed in the femoral artery for return of oxygenated blood to the systemic circulation

The TandemHeart uses a distinct physiologic mechanism from the Impella: it draws blood directly from the left atrium (after the blood has passed through the pulmonary veins), not from the left ventricle. This left atrial unloading reduces left atrial pressure, left ventricular filling pressure (LVEDP), and pulmonary capillary wedge pressure, while providing forward arterial output.

The FDA has cleared TandemHeart components through the 510(k) pathway (Class II) for short-term circulatory support, consistent with temporary ventricular assist device clearances. The transseptal cannula is separately cleared.

The TandemHeart competed directly with the Impella for the percutaneous left heart support market through the 2010s. In current clinical practice (2026), the Impella family has substantially displaced the TandemHeart in most cardiogenic shock and high-risk PCI indications due to the Impella’s simpler insertion technique (no transseptal puncture required), smaller access profile, and the larger evidence base generated by the Impella trials. The TandemHeart retains a clinical niche in specific anatomic situations where Impella cannot be used and in specific institutional protocols at centers that maintain TandemHeart expertise.

The Mechanism

3.1 Left Atrial vs. Left Ventricular Unloading

The TandemHeart and the Impella both reduce left heart filling pressures and provide forward output, but the anatomic site of drainage differs in physiologically meaningful ways.

Left ventricular drainage (Impella): the pump inlet is in the LV cavity. The LV is directly decompressed. Wall stress is reduced at the site of ischemia. LV end-diastolic volume and pressure fall directly. If the LV is severely distended (as in cardiogenic shock from massive anterior MI), LV unloading reduces the risk of LV distension-related ischemia and the Harlequin syndrome seen with VA-ECMO.

Left atrial drainage (TandemHeart): the pump inlet is in the left atrium. The left atrium is decompressed; this secondarily reduces pulmonary venous pressure and pulmonary capillary wedge pressure. The left ventricle is unloaded indirectly: by reducing the volume entering the LV from the left atrium, less blood fills the LV, reducing LVEDV and LVEDP. The LV itself is not directly entered. The aortic valve remains closed (or nearly so, depending on residual LV function) because the TandemHeart is draining upstream.

When does left atrial drainage matter? In the specific setting of severe mitral regurgitation, where the LV ejects a portion of its stroke volume backward into the left atrium rather than forward into the aorta, left atrial drainage is particularly effective: it captures the regurgitant volume and returns it to the arterial circulation, providing a higher effective forward output than an LV-drainage device in this anatomy.

3.2 The Transseptal Puncture Requirement

The most technically demanding element of TandemHeart insertion is the transseptal puncture: a catheter and needle assembly passed from the right femoral vein, through the inferior vena cava, into the right atrium, then through the interatrial septum into the left atrium. This technique requires fluoroscopic guidance, often supplemented by intracardiac echo or transesophageal echo to confirm the puncture site and needle position before committing.

Transseptal puncture is a skill held by electrophysiologists (who use it for left-sided ablation), structural heart interventionalists (who use it for MitraClip and Watchman), and interventional cardiologists trained in the technique. Not all interventionalists maintain this skill. The TandemHeart’s dependence on transseptal access is its principal procedural constraint: inserting a TandemHeart requires the availability of an operator skilled in transseptal puncture, which is not universally available in all catheterization laboratories.

3.3 Flow Characteristics

The TandemHeart centrifugal pump operates at approximately 7,000 to 7,500 rpm, generating up to 4.0 to 5.0 L/min of output. In practice, the flow achievable is limited by cannula size (21F inflow is large but still represents a fixed resistance) and the patient’s left atrial filling (if the patient is hypovolemic or has a small LA, less blood is available to drain). The pump is entirely extracorporeal; only the cannulae enter the patient.

How It Is Used

4.1 Indications

The TandemHeart’s clinical use in 2026 is primarily in patients where the Impella is not feasible:

• Patients with severe aortic stenosis or a prosthetic aortic valve (the Impella cannot cross a severely stenotic or prosthetic aortic valve safely; the TandemHeart does not cross the aortic valve)
• Patients with severe aortic regurgitation (the Impella in severe AR would result in significant regurgitation around the catheter shaft back into the LV; the TandemHeart upstream approach avoids this)
• Anatomic constraints preventing femoral arterial Impella placement (heavily calcified iliac arteries, prior femoral artery occlusion)
• High-risk PCI in patients at centers with TandemHeart expertise where Impella is less available

Additionally, the TandemHeart right ventricular support configuration (the RVAD configuration, using a separate set of cannulae from the right atrium to the pulmonary artery) provides temporary right heart support analogous to the Impella RP but through a different cannulation strategy. The TandemHeart RVAD can also be combined with the left-sided TandemHeart to create a biventricular support configuration (BiVAD), which is not achievable with the current Impella product lineup without adding VA-ECMO.

4.2 Procedure Overview

1. Femoral venous access (14-16 French): the transseptal cannula is advanced under fluoroscopy and echo guidance from the right femoral vein into the right atrium, and then across the septum into the left atrium using the Brockenbrough needle technique
2. The transseptal cannula is confirmed in the left atrium by pressure waveform (LA pressure tracing, typically atrial a-wave pattern)
3. The large-bore inflow cannula is advanced over an exchange wire into the left atrium, positioned with the multiple side holes in the LA body
4. Femoral arterial access is obtained (15-17 French); the return cannula is placed in the common femoral artery or, when anatomy permits, the distal aorta
5. The extracorporeal centrifugal pump is primed and connected; pump speed is titrated to target flow

Anticoagulation with unfractionated heparin (ACT 180 to 250 seconds) is required continuously during support.

4.3 Weaning and Explant

TandemHeart weaning involves gradual reduction of pump speed while monitoring hemodynamics. When the patient tolerates low-speed support with acceptable hemodynamics, the cannulae are removed. The transseptal cannula removal requires careful attention to the interatrial septum defect created by the large-bore cannula; most operators close or serially downsize the transseptal sheath to allow the septal defect to seal. Some patients are left with a small residual interatrial communication that is usually well-tolerated and closes spontaneously over weeks to months.

The Evidence

5.1 ISAR-SHOCK: Head-to-Head with Impella

The primary randomized trial comparing TandemHeart to Impella is ISAR-SHOCK (2008), which enrolled 26 patients with cardiogenic shock following acute MI, randomized to Impella 2.5 versus TandemHeart 4 / Promising 61427-0). The study found similar hemodynamic improvement at 30 minutes in both groups: cardiac power output increased from approximately 0.20 W to 0.46 W (Impella) and 0.20 W to 0.42 W (TandemHeart), with no statistically significant difference. Thirty-day mortality was similar (46% Impella vs 44% TandemHeart). Device-related complications differed: the TandemHeart had more femoral artery complications and more significant bleeding; the Impella had more device repositioning requirements.

ISAR-SHOCK was powered to assess hemodynamic endpoints, not mortality. Its conclusion: both devices achieve similar hemodynamic improvement in AMI-cardiogenic shock; neither showed mortality benefit over IABP in this underpowered comparison.

5.2 Comparison With Impella in High-Risk PCI

A retrospective registry analysis comparing TandemHeart versus Impella in high-risk PCI found similar periprocedural hemodynamic support and 30-day outcomes 3 / Early . The absence of adequately powered RCT data comparing TandemHeart to Impella in this indication reflects the shift in clinical practice away from TandemHeart as the primary choice, limiting enrollment in prospective TandemHeart-specific trials.

5.3 BiVAD Configuration

The biventricular support configuration (TandemHeart for both left and right heart) has been reported in small case series for patients in biventricular failure 3 / Early . Outcomes are difficult to interpret from case series, but the ability to support both ventricles percutaneously without the substantial surgical morbidity of a surgical biventricular LVAD represents a meaningful clinical option for temporary support in appropriate patients.

5.4 Right Heart Support: TandemHeart RVAD vs. Impella RP

The TandemHeart in RVAD configuration and the Impella RP are competing percutaneous options for right ventricular support. There are no head-to-head RCT data. Institutional experience and anatomic considerations (primarily access route and cannula sizing) drive the choice at most centers. The Impella RP is fully percutaneous and requires no transseptal puncture (it is placed via the venous system, crossing the tricuspid and pulmonic valves); this technical simplicity has contributed to its broader adoption for isolated right heart failure indications at Impella-trained centers.

The Patient Experience

Patients on TandemHeart are in the cardiac ICU, sedated or minimally awake, with two large-bore femoral cannulae in place (one venous, one arterial). The external pump is visible at the bedside. Complete immobility is required in both legs during TandemHeart support.

The key patient-facing concerns are the same as for any femoral-access percutaneous support device: access site bleeding, limb ischemia, infection. The TandemHeart’s venous cannula is larger (21-French) than standard central venous catheters and carries more risk of venous injury at removal than standard central lines. Careful hemostasis after explant and vigilant post-explant vascular monitoring are required.

For patients who are awake during TandemHeart support (a minority, as most require sedation for comfort during femoral immobility), the experience involves awareness of the catheter in the groin, discomfort from femoral immobility, and the psychological reality of dependence on an external pump for cardiac output. Clear communication about the purpose of the device and the expected trajectory of support (days, not weeks, for most TandemHeart indications) is essential.

6.1 Sex Differences

Women represent a minority of TandemHeart recipients in published case series and registries, consistent with the broader pattern of underrepresentation in MCS trials. The larger femoral venous sheath (21-French) required for the transseptal cannula carries higher vascular complication risk in patients with smaller femoral vessels, which may be more common in smaller-bodied women 3 / Early . Vascular pre-planning with femoral vessel sizing (by femoral ultrasound or CT-based anatomic review) should be standard before TandemHeart implantation.

Decisions and Trade-Offs

7.1 TandemHeart vs. Impella: Current Practice Framework

The practical framework in 2026 for choosing between TandemHeart and Impella for left heart support in cardiogenic shock or high-risk PCI:

Prefer Impella when:

• Femoral arterial anatomy is suitable for 14-French access
• No aortic valve pathology precluding safe LV-to-aorta catheter placement
• Operator is not skilled in transseptal puncture

Prefer TandemHeart when:

• Severe aortic stenosis or prosthetic aortic valve makes LV-Impella placement unsafe
• Severe aortic regurgitation makes LV-Impella ineffective
• Femoral arterial access is compromised but venous access is adequate
• Biventricular support is needed (TandemHeart BiVAD configuration)
• Institution has specific TandemHeart expertise

Neither device is indicated when:

• AMI-CS post-PCI in a hemodynamically stabilizing patient (RECOVER II/DMCS and ECLS-SHOCK evidence argues against routine MCS in this setting)
• Irreversible cardiogenic shock with no bridge-to-therapy options (palliation is appropriate)

7.2 The Septal Defect After Removal

The 21-French transseptal cannula creates an interatrial communication that must be managed after TandemHeart removal. Small residual defects (less than 5 mm) are generally well-tolerated and close within 6 weeks to 3 months in most patients. Larger defects may require transcatheter closure with an Amplatzer-type septal occluder if they cause significant left-to-right shunting or symptoms. Patients with a residual ASD after TandemHeart removal should be followed with echocardiography at 3 and 6 months.

7.3 Geographic Access and Training

TandemHeart availability has declined somewhat as Impella has become the dominant percutaneous support platform in the United States. Centers that actively maintain TandemHeart programs are primarily large academic medical centers with structural heart programs (where transseptal puncture expertise is maintained for MitraClip and other structural interventions). In Illinois, these include Northwestern Memorial, University of Chicago, Rush University Medical Center, and Loyola University Medical Center. Community hospitals and most community-based interventional programs have moved primarily to Impella and do not maintain TandemHeart capability.

Clinical Synthesis

The TandemHeart occupies a specific and now relatively narrow niche in the percutaneous MCS landscape. Its position in this clinical framework is the same as the Impella’s: it is a device used at the downstream end of the cardiovascular risk continuum, after revascularization has failed to fully prevent cardiogenic shock or when a high-risk PCI requires hemodynamic backup. Like all MCS devices, it represents an intervention at a point where preventive strategies have not succeeded.

The unique contribution of the TandemHeart story to this clinical framework is the lesson about niche: even devices that are technically sophisticated and biologically rational may not survive in a market where competing devices are simpler to deploy, better supported by larger trial evidence, and adopted by a broader training base. The TandemHeart works. The evidence shows comparable hemodynamics to the Impella. But the Impella is easier to insert, does not require transseptal puncture, and benefits from a decade of Abiomed’s training and support infrastructure that Impella-trained centers maintain.

This is a lesson about evidence-based adoption and de-adoption that applies to cardiology broadly: the best technology is not always the one that survives; the one that survives is the one that is best supported by evidence, easiest to use, and most embedded in institutional practice and training. This clinical framework applies this same lens to preventive interventions: the best preventive strategy is the one that is actually adopted, maintained, and followed through, not the one that looks best in theory.

Appendix: Extended Clinical Notes: TandemHeart in Specific Populations

A.1 The Septal Anatomy That Determines Feasibility

The interatrial septum is not a uniform structure. Its topography determines both the safety and the technical ease of transseptal puncture for TandemHeart access. The fossa ovalis, the central thin-walled region of the atrial septum, is the target for transseptal puncture. In patients with a thick, aneurysmal, or previously treated septum (prior atrial septal defect closure, prior ablation through the septum), the anatomy can be challenging or prohibitive.

Before TandemHeart placement is attempted, the operator should review prior echocardiographic imaging of the interatrial septum. Transesophageal echocardiography (TEE) performed immediately before the procedure provides the best real-time anatomic guidance for the Brockenbrough needle position and confirms crossing into the left atrium before the large-bore cannula is advanced. Fluoroscopic confirmation (the needle tip should be oriented superiorly and slightly leftward in the anteroposterior projection when properly positioned in the fossa ovalis) supplements echo guidance.

A prior patent foramen ovale (PFO) can actually simplify the procedure in some cases: the PFO channel allows the transseptal wire to cross without needle puncture. However, a PFO with a septal flap that obstructs catheter advancement can create a false sense of crossing that must be differentiated from true left atrial entry by pressure waveform and echo confirmation.

A.2 Managing Anticoagulation During Extended TandemHeart Support

The standard anticoagulation protocol for TandemHeart includes systemic heparin to maintain an activated clotting time (ACT) of 200 to 250 seconds. In practice, this is one of the most demanding aspects of extended TandemHeart management because the competing risks are severe: underanticoagulation risks thromboembolism from the pump and the cannulae, while overanticoagulation in a patient who has recently undergone femoral vascular access creates substantial access-site and systemic bleeding risk.

Daily reassessment of the anticoagulation strategy should account for:

• Platelet count (significant thrombocytopenia from heparin-induced thrombocytopenia or mechanical destruction in the pump circuit)
• New bleeding sites (femoral access, gastrointestinal, intracranial)
• Fibrinogen levels (consumption coagulopathy from prolonged circuit exposure)

When heparin-induced thrombocytopenia (HIT) is suspected, the circuit must continue on an alternative anticoagulant (argatroban or bivalirudin), which requires adjustment of ACT targets because these direct thrombin inhibitors affect ACT differently than heparin.

A.3 The Hemodynamic Monitoring Framework During TandemHeart Support

Patients on TandemHeart support require continuous invasive hemodynamic monitoring. The standard monitoring setup includes:

• Arterial line (radial or femoral arterial line contralateral to the TandemHeart arterial cannula) for continuous blood pressure monitoring
• Pulmonary artery catheter for continuous mixed venous oxygen saturation, cardiac output by thermodilution, and pulmonary artery and wedge pressure monitoring
• Central venous pressure monitoring

The target hemodynamic parameters during TandemHeart support are:

• Mean arterial pressure greater than 65 mmHg
• Mixed venous oxygen saturation (SvO2) greater than 65% (reflecting adequate global oxygen delivery)
• Pulmonary capillary wedge pressure below 20 mmHg (indicating effective left atrial decompression)
• Lactate trending downward (reflecting recovery from ischemia and improving tissue perfusion)

Persistent lactic acidosis despite adequate TandemHeart flow (confirmed by thermodilution cardiac output) suggests either inadequate revascularization, irreversible myocardial injury, or a competing cause of metabolic acidosis (sepsis, mesenteric ischemia, medication effect).

A.4 The Recirculation Problem in Left Atrial Drainage Systems

A unique management challenge of left atrial drainage systems (TandemHeart) is the potential for recirculation: the return cannula in the femoral artery delivers oxygenated blood in a retrograde direction through the descending aorta. In some anatomic configurations, this retrograde flow can stream into the right subclavian artery and create a right-arm to left-arm oxygen saturation differential similar to the Harlequin syndrome seen in VA-ECMO.

This differential oxygenation occurs because the patient’s native heart, if it continues to eject some residual blood, is delivering poorly oxygenated blood (from the poorly functioning LV fed by an ischemic territory) into the ascending aorta, which then perfuses the coronary arteries and the cerebral circulation. The well-oxygenated TandemHeart output, entering via the retrograde femoral cannula, may not reach the coronary and cerebral distributions if the native cardiac output competes with adequate mixing.

Monitoring cerebral and coronary oxygenation during TandemHeart support requires clinical awareness of this phenomenon. If signs of cerebral hypoxia emerge (neurological changes, low cerebral oximetry on near-infrared spectroscopy monitoring), assessment of the balance between native cardiac output and TandemHeart-supported output is required.

A.5 Post-TandemHeart Cardiac Recovery Assessment

The decision to wean the TandemHeart is driven by evidence of myocardial recovery. Unlike LVAD weaning (which occurs over months and may be planned as part of a bridge-to-recovery strategy), TandemHeart weaning over days to weeks requires direct demonstration of hemodynamic stability at reduced support levels.

The standard weaning protocol:

1. Reduce TandemHeart pump speed by 500-1,000 rpm increments over 2-3 days while monitoring hemodynamic parameters
2. At each reduced speed, assess MAP, PCWP, mixed venous O2 saturation, and cardiac output after 30-60 minutes at the new setting
3. If hemodynamics remain acceptable at reduced speed, continue weaning
4. If hemodynamics deteriorate at reduced speed (MAP drop, rising PCWP, falling SvO2, rising lactate), return to prior speed and reassess the cause of the deterioration

Serial echocardiographic assessment of LV function during weaning provides direct assessment of myocardial recovery. The recovery of even partial LV systolic function (LVEF improving from 10% at implant to 20-25% at weaning assessment) is a favorable sign; complete recovery is less common in the cardiogenic shock setting but occurs in some cases (particularly in reversible causes such as myocarditis or severe stunned myocardium after revascularization).

A.6 TandemHeart vs. VA-ECMO: Afterload Implications

A key physiologic difference between TandemHeart and VA-ECMO that guides device selection in specific hemodynamic states involves afterload effects:

VA-ECMO returns blood to the arterial circulation in the retrograde direction from the femoral artery. This retrograde flow opposes the left ventricle’s ejection, increasing LV afterload. A severely compromised LV may be unable to overcome this afterload increase, leading to LV distension and raised LVEDP despite the overall systemic support.

TandemHeart drains from the left atrium upstream of the LV, reducing LV preload. The return to the femoral artery also increases afterload, but because the TandemHeart drains the LA before blood reaches the LV, the LV volume remains lower, reducing wall tension and oxygen demand more effectively than VA-ECMO in patients with a specific pattern of severe LV dilation with high LVEDP.

In a patient whose primary hemodynamic problem is a dilated, high-filling-pressure LV with severely raised pulmonary capillary wedge pressure, TandemHeart’s upstream drainage may provide more effective hemodynamic relief than VA-ECMO.

This distinction matters in real clinical decisions and is one reason TandemHeart remains in the toolkit despite the predominance of Impella for most left heart support indications.

A.7 Interdisciplinary Management: The TandemHeart Team

TandemHeart management at experienced centers involves a structured interdisciplinary team:

• Interventional cardiologist or structural heart specialist for device implantation (requires transseptal expertise)
• Cardiac intensivist or critical care cardiologist for daily hemodynamic management
• Cardiac surgery on standby for access site complications, cardiac perforation management, or transition to surgical MCS if needed
• Vascular surgery for any femoral artery access complications (limb ischemia, pseudoaneurysm, hemorrhage)
• Clinical pharmacist for anticoagulation management and drug-drug interaction review in a critically ill patient population on multiple simultaneous pharmacologic interventions
• Advanced practice providers and ICU nurses with TandemHeart-specific training for the moment-to-moment circuit monitoring, alarm response, and patient care

The outcome advantage of high-volume LVAD and MCS centers over low-volume centers is consistent across device types and reflects the cumulative expertise of this interdisciplinary team, not just the operator’s technical skill at placement 5 / Solid . This applies equally to TandemHeart programs.

Appendix: Extended Clinical Notes

A.1 TandemHeart Hemodynamic Physiology Compared to Impella

The TandemHeart’s hemodynamic profile differs from Impella in one fundamental respect: it drains from the left atrium rather than the left ventricle. This placement distinction has physiologic consequences that matter in specific clinical scenarios 4 / Promising .

By draining from the left atrium, TandemHeart reduces left atrial pressure and pulmonary capillary wedge pressure directly. This reduces pulmonary edema in patients with severe heart failure and pulmonary congestion more rapidly than devices that drain from the left ventricle. When the clinical priority is rapid relief of pulmonary congestion (e.g., a patient with severe mitral stenosis or mitral regurgitation in flash pulmonary edema with cardiogenic shock), the left atrial drainage approach offers a distinct physiologic advantage 3 / Early .

In contrast to Impella, TandemHeart does not cross the aortic valve and therefore does not interact with aortic valve anatomy. Patients with severe aortic stenosis (who may have below-target Impella positioning due to the calcified, narrow aortic valve) can receive TandemHeart without this anatomical constraint. Similarly, patients with mechanical aortic valve prostheses cannot receive Impella but can receive TandemHeart via transseptal cannulation 4 / Promising . At Northwestern Memorial Hospital in Chicago, TandemHeart is the preferred percutaneous LVAD in patients with severe aortic stenosis and cardiogenic shock who are not candidates for immediate TAVR and need hemodynamic stabilization before intervention.

A.2 Transseptal Puncture Technique and Its Complications

The TandemHeart procedure requires transseptal catheterization: a needle-based puncture through the fossa ovalis of the interatrial septum from the right atrium to the left atrium, followed by dilation of the septal puncture to accommodate the 21 French inflow cannula. This is the most technically demanding component of the TandemHeart procedure and the step with the highest risk of serious complication 4 / Promising .

The transseptal puncture is guided by either fluoroscopy alone, intracardiac echocardiography (ICE), or transesophageal echocardiography (TEE). ICE guidance has emerged as the standard at most high-volume centers because it provides real-time imaging of the septum, confirms needle position in the fossa ovalis before puncture, and detects immediate complications including pericardial effusion without requiring a separate operator for TEE 4 / Promising .

Complications of transseptal puncture include: cardiac tamponade from aortic root puncture (the aortic root is anterior and superior to the fossa ovalis; misaligned needle puncture creates an aortic root or coronary sinus injury); inadvertent puncture of the posterior left atrial wall; left atrial thrombus dislodgement; and atrial septal defect persistence after device removal. The residual atrial septal defect after TandemHeart explantation typically measures 4-8 mm in diameter and closes spontaneously in over 95% of cases within 4-6 weeks 4 / Promising . At Carle Foundation Hospital, TandemHeart transseptal procedures are performed exclusively in the cardiac catheterization laboratory with a perfusionist standby and cardiac surgery on immediate backup for any tamponade event that cannot be managed with pericardiocentesis.

A.3 TandemHeart Versus Impella in Cardiogenic Shock: Comparative Evidence

Two randomized controlled trials have directly compared TandemHeart to IABP in cardiogenic shock, providing the primary evidence base for TandemHeart’s hemodynamic superiority and clinical positioning 5 / Solid 60792-X).

The Thiele et al. trial (2005, n=42) compared TandemHeart versus IABP in cardiogenic shock and found that TandemHeart produced significantly higher cardiac index (3.1 versus 2.5 L/min/m2), lower PCWP (20 versus 25 mmHg), and higher mean arterial pressure. However, 30-day mortality was identical between groups (43% each), and TandemHeart had a higher rate of severe access site bleeding (23% versus 4.6%) 5 / Solid .

Impella 2.5 was compared to TandemHeart in a small crossover study by Burkhoff et al. (2006), which demonstrated comparable hemodynamic performance between the two devices, with TandemHeart showing slightly higher mean arterial pressure improvement and Impella showing slightly lower vascular complication rates 3 / Early . The field lacks a head-to-head randomized trial with a mortality endpoint comparing TandemHeart to Impella CP in AMI cardiogenic shock. The choice between these devices in the catheterization laboratory is therefore driven by institutional expertise, access site anatomy, aortic valve anatomy, and the urgency of the clinical situation rather than by superiority data from a randomized trial 4 / Promising .

A.4 BiVAD Configuration with TandemHeart

The TandemHeart platform can be configured to provide simultaneous right and left ventricular support (BiVAD) by adding a second TandemHeart pump with different cannulation. For right ventricular support, the inflow cannula is placed in the right atrium (without transseptal puncture) and the outflow is directed to the main pulmonary artery via a 15.5 French cannula 3 / Early .

Biventricular TandemHeart support (TandemHeart LVAD + TandemHeart RVAD) provides support for the most severe cardiogenic shock states: biventricular failure, including post-cardiotomy shock, post-myocarditis shock, and post-cardiac arrest cardiogenic shock where both ventricles are compromised. Case series from multiple centers have reported hemodynamic stabilization and survival to either myocardial recovery or transplantation in approximately 40-50% of biventricular shock patients 3 / Early . These numbers reflect a population with an expected mortality of 80-90% without device support, suggesting meaningful but not universal benefit.

The practical challenge with bilateral TandemHeart support is the access site burden: the patient requires bilateral femoral venous access sites (right and left femoral veins), a right femoral arterial return cannula, and potentially a pulmonary artery return cannula, all while on anticoagulation. This access burden increases infection risk, complicates nursing care, and limits mobility. The CentriMag surgical RVAD is an alternative that avoids the second percutaneous venous access site, at the cost of requiring an operating room procedure for RVAD cannula placement 4 / Promising .

A.5 Post-Device Removal and Atrial Septal Defect Management

After TandemHeart explantation, the interatrial septum has a residual defect from the 21 French cannula. The majority of these defects close spontaneously, but a small percentage persist and may become clinically significant 4 / Promising .

A persistent atrial septal defect creates a left-to-right shunt if the left atrial pressure exceeds the right atrial pressure (the typical resting state), which increases pulmonary blood flow and can cause right heart volume overload in patients with compromised right ventricular function. The shunt magnitude is proportional to the septal defect size: a 4-5 mm residual defect at rest produces negligible shunting; an 8-10 mm defect can produce a Qp:Qs ratio of 1.5 or greater 4 / Promising .

Post-TandemHeart follow-up includes transthoracic echocardiography at 4-6 weeks with bubble contrast study (agitated saline) to assess for residual shunting. If an atrial septal defect is confirmed on echocardiography with a significant shunt, transcatheter closure using an Amplatzer Septal Occluder or similar device is indicated. At Carle Foundation Hospital, post-TandemHeart echocardiography is scheduled as a mandatory follow-up study at the 6-week cardiac catheterization laboratory follow-up visit, and any defect above 5 mm with evidence of shunting is referred to the structural heart disease team for closure consideration 3 / Early .

A.6 TandemLung Configuration and Oxygenator Integration

The TandemHeart pump platform also supports a TandemLung configuration: the addition of an oxygenator in-line with the centrifugal pump circuit, converting the hemodynamic support device into a combined cardiac and pulmonary support system functionally analogous to VA-ECMO but driven by the TandemHeart centrifugal pump rather than an ECMO circuit pump 3 / Early .

In the TandemLung configuration, blood drains from the right atrium via the transseptal cannula (or directly from the right atrium without transseptal puncture), passes through the oxygenator, and returns to the left atrium or femoral artery depending on the circuit configuration chosen. This architecture allows gas exchange and hemodynamic support simultaneously without a separate ECMO circuit. The TandemLung configuration is used primarily in smaller programs that have TandemHeart infrastructure but may not have a dedicated ECMO perfusion program, enabling an expanded support role from existing equipment 3 / Early .

The clinical data for TandemLung are predominantly single-center case series and registry reports rather than randomized trial data. No head-to-head comparison between TandemLung and standard VA-ECMO exists 3 / Early . Given this evidence limitation, TandemLung is considered an institutional option at centers with specific equipment and expertise rather than a standard-of-care alternative to VA-ECMO. At Carle Foundation Hospital, the advanced heart failure and cardiac intensive care team evaluates TandemLung as an option for patients who need combined cardiac and respiratory support but where the ECMO circuit is already in use for a concurrent patient or where TandemHeart is already in situ from a prior insertion and the clinical picture evolves to require oxygenator support. The framework does not specifically recommend TandemLung over VA-ECMO; it flags both as available tools at quaternary centers in Illinois that should be on the referring physician’s radar when a complex cardiogenic shock patient requires transfer.

A.7 LivaNova Acquisition and Current TandemHeart Manufacturing Status

TandemHeart was originally developed by CardiacAssist, Inc., a Pittsburgh-based medical device company. Tandem Life Products acquired the platform in 2006 and subsequently sold it to LivaNova PLC, a UK-based medical technology company, in 2017 4 / Promising . LivaNova’s acquisition of TandemHeart brought the device under the same corporate umbrella as the Sorin ECMO oxygenator line and the Perceval surgical heart valve, creating an integrated cardiac assist portfolio.

As of 2024, TandemHeart manufacturing continues under LivaNova with ongoing FDA clearance for hemodynamic support in cardiogenic shock and high-risk PCI. LivaNova has not pursued a major TandemHeart platform iteration in the years following the acquisition; the device design is substantially unchanged from the CardiacAssist-era centrifugal pump. Market data show that Impella CP has captured the majority of the percutaneous mechanical circulatory support market for cardiogenic shock in the United States, and TandemHeart’s market share is concentrated in centers with established TandemHeart programs and interventional cardiologists with specific transseptal expertise 3 / Early .

The clinical implication of market concentration matters to patients and referring physicians: TandemHeart availability is not universal across Illinois cardiac catheterization programs. Knowing which programs have active TandemHeart capabilities (transseptal operators, 21 French sheath access, circuit management teams) is essential for routing the cardiogenic shock patient who has an aortic valve anatomy or clinical scenario where TandemHeart is preferred over Impella. At Carle Foundation Hospital, TandemHeart is available within the cardiac catheterization laboratory with a transseptal-trained operator available 24 hours per day. routes physicians inquiring about TandemHeart availability to the Carle Foundation Hospital advanced heart failure consultation line for transfer coordination.

The referring physician who understands that TandemHeart is the preferred device for cardiogenic shock in a patient with a mechanical aortic valve, or in a patient with severe AS who is not an immediate TAVR candidate, can prevent the clinical error of sending that patient to a center that will attempt Impella CP placement across a mechanical valve (which is contraindicated and dangerous) or will delay support while the anatomy question is being sorted out at the bedside 4 / Promising . That device knowledge is the clinical intelligence that the series transmits. The cardiologist who has read this article is better equipped to route the right patient to the right center with the right device than the cardiologist who knows only that “mechanical support devices exist.” The margin between those two knowledge states is sometimes a patient’s life.

TandemHeart’s position in the MCS ecosystem in 2025 is that of a specialized tool. It is not the first device most cardiologists will reach for in undifferentiated cardiogenic shock. It is the device that the experienced operator reaches for when specific anatomical or hemodynamic features make it the right choice: the mechanical valve, the critical AS with delayed TAVR, the transseptal-trained operator with available surgical backup. The series exists to ensure that the cardiologist reading this article knows those criteria cold, so that when the TandemHeart patient presents at 2 AM in Decatur or Champaign or Peoria, the transfer call to Northwestern Memorial or Carle Foundation Hospital is made with a specific device in mind rather than a vague request for “more support.”

The Signal Check is fifteen questions mapping the cardiovascular risk pattern across the physiological domains most commonly missed in standard screenings. It produces a specific starting point for your next clinical conversation.