Single-Center Experience with the TandemHeart Percutaneous<br />
Ventricular Assist Device to Support Patients undergoing<br />
High-Risk

Percutaneous coronary intervention (PCI) offers an alternative form of therapy for patients considered to be at high risk for coronary artery bypass graft surgery (CABG). PCI is associated with substantial morbidity and mortality in the presence of significant comorbidities such as poor left ventricular function.^1–5 High-risk PCI (such as left main [LM] percutaneous intervention and/or PCI in the setting of severe left ventricular dysfunction) has been performed using various modalities for circulatory support including intra-aortic balloon pump (IABP) counterpulsation^6–8 and extracorporeal membrane oxygenation.^9,10
We report our clinical experience with the use of the TandemHeart Percutaneous Ventricular Assist Device (THp- VAD) (CardiacAssist, Inc., Pittsburgh, Pennsylvania) as a method to provide circulatory support during high-risk PCI of complex multivessel coronary artery disease (CAD). Patients who undergo PCI with severe left ventricular systolic dysfunction, complex coronary artery lesions, i.e., LM CAD (or its equivalent) or bypass grafts, who are at a higher risk of an adverse outcome due to circulatory collapse in the setting of ischemia from balloon inflations, coronary artery dissections, abrupt vessel closure or no-reflow.¹¹ Although IABP has been used in unstable patients for mechanical and hemodynamic support during PCI, this modality only modestly augments cardiac output and coronary blood flow, and may not provide maximal circulatory support.¹² The THpVAD may enable the physician to perform high-risk PCI while minimizing the potential risk for circulatory collapse.¹

Patients and Methods
Patients. Between December 2005 and May 2007, 6 patients received circulatory support with the THpVAD during high-risk PCI. Each patient’s coronary anatomy was complex and PCI was considered to be associated with significant hemodynamic compromise. These patients were considered to be too high of a risk for CABG because of depressed left ventricular function, significant pulmonary disease, previous sternotomies or other significant comorbidities.
There were 5 males and 1 female. The average age of the patients was 69 years (range: 62–81 years). The average left ventricular ejection fraction was 33% (range 15–65%). All patients had significant (> 75% angiographic stenosis) LM CAD (Table 1). Five of the 6 patients underwent unprotected LM PCI. The time recorded to insert the pVAD was measured in all 5 patients (Table 2). Transseptal puncture was performed in the usual fashion and was confirmed both fluoroscopically and by intracardiac echocardiography. Once the ideal flow rate was achieved, PCI was performed. A vascular surgeon removed the pVAD when weaning was successful. Before each procedure, each patient and their family gave written, informed consent to undergo PCI facilitated with the use of the THpVAD.
Device description. The TandemHeart pump takes oxygenated blood from the left atrium through a 22 Fr cannula and returns it to a 16 Fr femoral artery cannula. The pump provides continuous nonpulsatile blood flow at a rate of 4.0–5.0 liter/minute. Cooling and lubrication of the spinning rotor are provided by 10 cc/hour of heparinized saline flush above the seal which separates the rotor chamber from the blood chamber. Heparin is used to prevent clot formation. The ideal activated clotting time (ACT) is 250–350 seconds. The Mobile Tandem- Heart Controller monitors and regulates the blood flow rate and the lubrication fluid in the pump system (Figure 1).

Revascularization procedure. The patients were prepared and draped in the usual sterile fashion. An 11 Fr side-arm sheath was placed via a modified Seldinger technique in the left common femoral vein. A second 6 Fr side-arm sheath was placed in the left common femoral artery. An 8 Fr side-arm sheath was placed in the right common femoral vein, and a 6 Fr side-arm sheath was placed in the right common femoral artery. An intracardiac echocardiography probe was advanced through the left 11 Fr common femoral vein sheath and placed in the right atrium to assess the atrial septal wall. A Brockenbrough needle was inserted into an 8 Fr Mullins sheath in the right common femoral vein and advanced into the right atrium under fluoroscopic guidance. We then placed a 5 Fr pigtail catheter into the ascending aorta to mark the aorta in order to avoid any complications while performing the transseptal puncture. The Brockenbrough needle was retracted into an optimum position, confirmed by fluoroscopy and intracardiac echocardiography. Next, transseptal puncture was performed. The Mullins sheath was advanced into the left atrium and heparin was delivered intravenously to achieve an activated clotting time of 250–350 seconds.
Preparations were made for percutaneous THpVAD placement. The Brockenbrough needle was removed and an Inoue wire was placed in the left atrium (Figure 2). Next, the pVAD conduit was placed through the right common femoral vein into the right atrium across the septal wall into the left atrium (Figure 3). A 17 Fr arterial conduit was placed in the left common femoral artery. Both cannulae were primed with the patient’s own blood, and following saline priming of the VAD, both cannulae were attached to the device. There was no “chatter”, and ideal placement was confirmed by intracardiac echocardiography and fluoroscopy (Figure 4).

Results
All 6 patients survived the high-risk PCI facilitated with the pVAD. One patient (#6) died of multiorgan failure 3 days after the PCI. Placement of the pVAD, which required transseptal cannulation and access to the left atrium, was successful in all 6 patients. One patient (#4) had an inferior vena cava filter (IVCF) that did not impede the placement of the inflow cannula. Patient #4 also had an occluded right external iliac artery, thus the outflow cannula was placed in the left femoral artery and PCI was performed through the left brachial artery. One patient (#1) experienced a transient, but self-limited, neurological event that was assessed by a consulting neurologist to be a possible seizure.
Revascularization was successful in all patients (Table 1). The pVAD provided adequate circulatory support during all high-risk PCI procedures. The average pump flow rates were 3.4 l/minute; the average time required to place the pVAD was 36.5 minutes. A vascular surgeon in the operating room removed all 6 of the devices. All removals were successful without significant groin complications. Five of the 6 patients were discharged 30 days after the procedure from the hospital.

Discussion
High-risk PCI can be facilitated with IABP, but may provide only minimal circulatory support in the setting of complete hemodynamic collapse.¹³ One of the main limitations of IABP is the lack of active cardiac support and a requirement for a certain level of left ventricular function. The potential maximum cardiac output that an IABP can achieve is about 1.5 L/minute. In our series of patients, we achieved an average flow rate of at least 3 L/minute. Hence, all of our patients may not have had the necessary safety margin required for high-risk PCI in the absence of the pVAD. In the era of improved equipment design, direct stenting techniques and antiplatelet drug therapy, there has been improvement in the procedural success rate of high-risk PCI.¹⁴ In 2001, the randomized, controlled trial, Angina with Extremely Serious Operative Mortality Evaluation (AWESOME)15, compared CABG and PCI survival among patients with medically refractory ischemia who had undergone prior CABG, had a recent myocardial infarction (MI), a poorly functioning left ventricle or instability that necessitated IABP. This study revealed comparable 3-year survival rates between the two groups.

The left ventricular assist device (LVAD), which requires surgical implantation, has been shown to reduce the extent of myocardial necrosis when compared to controls.^11,16 However, the routine use of a LVAD in the setting of acute MI and cardiogenic shock requires resources and experienced personnel.^11,17 Also, in patients with acute MI, there was a 75% mortality rate with early LVAD implantation.¹⁸
The THpVAD enables the physician to provide an adequate level of circulatory support while performing high risk PCI. It is usually not associated with infection or hemolysis in most cases. Patients with small tortuous arteries or peripheral vascular disease may not accommodate the 15–17 Fr outflow cannula. Risks of pVAD implantation include rupture or perforation of either atrium during transseptal approach which may create a permanent atrial septal defect. The inflow cannula may also migrate back to the right atrium.
The benefits of the THpVAD in this small case series include an increase in the amount of time available for optimal balloon angioplasty and stent placement; it allowed us to perform a complex debulking procedure and we were able to perform LM PCI, or its equivalent, without circulatory collapse (Figure 5). However, device placement required a high level of skill and organization, and may be difficult to apply widely.

Conclusion

High-risk PCI in patients with significant comorbidities that may preclude them from CABG can be safe, effective and performed in an efficient manner when it is facilitated with the THpVAD. The patients in our series were evaluated by at least 2 physicians and were assessed as being either ineligible for surgery because of an unacceptably high operative mortality risk due to significant comorbidities, or simply refused surgery. The pVAD provided an adequate amount of circulatory support to perform long balloon inflation times and optimize the stent position in all patients. It was successfully placed in all 6 patients, and with removal of the device in the operating room by a vascular surgeon, groin complications were nonexistent.

References

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