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Use of the TandemHeart Percutaneous Ventricular Assist Device
to Support Patients Undergoing High-Risk Percutaneous Coronary In
March 2006
Although coronary artery bypass grafting (CABG) is the preferred treatment for disease in an unprotected left main coronary artery or left main equivalent, patients with serious comorbid conditions may be unsuitable for surgical intervention. Percutaneous coronary intervention (PCI) offers a nonsurgical approach for selected patients, but its morbidity and mortality rates can be unacceptably high in the presence of comorbidities, particularly poor left ventricular function.1–4 During high-risk PCI, physicians have used various methods of circulatory support, including intra-aortic balloon pump (IABP) counterpulsation5–7 and extracorporeal membrane oxygenation.8,9 We report our initial experience with the TandemHeart Percutaneous Ventricular Assist Device (pVAD) (CardiacAssist, Inc., Pittsburgh, Pennsylvania) (Figure 1) for supportive therapy during high-risk PCI. Designed for rapid percutaneous cannula insertion in the catheterization laboratory, this centrifugal pump provides up to 3.5 L/minute of continuous flow.
Patients and Methods
Patients. Between August 2003 and March 2004, we used the TandemHeart during PCI to support 5 consecutive patients who were ineligible for CABG because of decreased ventricular function, significant pulmonary disease or previous sternotomies. Moreover, because of the nature of the anatomy involved, each patient was at high risk for ischemic complications during PCI. Table 1 shows the patient data. The 4 men and 1 woman had an average age of 78 years (range: 70 to 84 years). Four patients had severe left main coronary artery lesions, and 1 patient had severe disease of a vein graft to the left anterior descending (LAD) artery, which was the sole conduit to the myocardium. Before undergoing the procedure, each patient gave informed, written consent for use of the TandemHeart. The investigators conformed to institutional guidelines and those of the American Physiological Society.
Device description. The TandemHeart pVAD is a continuous flow centrifugal pump designed to provide up to 3.5 L/minute of blood flow to the systemic circulation (Figure 1). The pump is placed in a neoprene holster that is secured to the patient’s thigh. The inflow cannula is inserted into the femoral vein percutaneously and advanced across the interatrial septum into the left atrium, and the percutaneously placed outflow cannula returns oxygenated blood to the femoral artery. A continuous infusion of heparinized saline solution (900 U/hour) provides a hydrodynamic bearing for the pump, as well as local anticoagulation and cooling of the motor. The inflow and outflow cannulas are connected to the pump with standard 3/8-inch polyvinyl chloride tubing. The pump requires a priming volume of 10 mL.
Revascularization procedure. After access to the left atrium was gained using a transseptal puncture technique, the interatrial septum was dilated with a two-stage, 14–21 Fr dilator. A 0.025 inch guidewire was introduced, and a 13 Fr obturator was used to advance the 21 Fr transseptal inflow cannula into the left atrium (Figures 2 and 3). The cannula’s position was verified with angiography (Figures 2A and 3A). A 15 Fr or 17 Fr outflow cannula was then placed in the femoral artery. After the pump was de-aired and the cannulas connected to the centrifugal pump, the pVAD was started at 2,500 to 3,000 rpm. The speed was gradually increased to provide a supplemental flow of 2 to 3 L/minute.
Immediately after pump insertion and initiation of support, PCI was performed according to standard techniques. All 5 patients underwent stent placement, and 1 patient also underwent rotational atherectomy (Figure 2B). Four patients were weaned from the pVAD shortly after undergoing PCI. The fifth patient continued to require support for 48 hours after the procedure.
In 3 cases, the catheters were removed and the vessels repaired surgically. Two of these procedures were performed in the catheterization laboratory at the end of the intervention, and 1 repair, in a patient who needed prolonged support, was performed in the operating room. Because of increased experience, we were able to perform the last 2 removal/repair procedures percutaneously at the end of the intervention using the PerClose® vascular closure device (Abbott Laboratories, Abbott Park, Illinois) according to the technique described by Howell and colleagues.10 During both procedures, a surgical team was on standby in the catheterization laboratory.
Individual cases. The first patient had a calcific lesion that could not be predilated in previous attempts with a small balloon and that required prolonged (2-minute) inflation with a noncompliant balloon before the lesion yielded. During the inflation period, the heart lost pulsatility and was supported by the TandemHeart completely.
The second patient had severe stenosis of the left main and proximal LAD arteries, an ejection fraction of 40%, and a severely depressed forced expiratory volume in 1 second (FEV1). He was supported by the TandemHeart during prolonged inflation of a noncompliant balloon.
The third patient had very long calcific left main and LAD lesions that required multiple prolonged inflations of a noncompliant balloon before stents could be placed. Again, during inflations, the heart lost contractility to such an extent that the aortic valve did not open, and the patient was dependent on TandemHeart support.
The fourth patient had an ejection fraction of ® distal protection device (Medtronic, Inc., Minneapolis, Minnesota), with interruption of the coronary circulation for more than 5 minutes. During this time the patient was entirely supported by the TandemHeart. Because of persistent poor left ventricular function, he required further support for 48 hours after treatment.
The fifth patient had a low ejection fraction and severely calcific left main and LAD arteries that required rotational atherectomy before they could be stented (Figure 2B). As expected, rotational atherectomy reduced the ejection fraction transiently, necessitating TandemHeart support.
Results
In all 5 cases, transseptal cannulation and initiation of support with the TandemHeart pVAD was successful, without serious complications. One patient had 70–80% bilateral stenoses of the common iliac arteries and required stenting of both arteries before placement of the pump cannulas. The average pump flow was 3 L/minute. Four patients were supported with the pVAD for an average of 107 minutes, support being discontinued shortly after PCI. Because of persistent poor left ventricular function, however, 1 patient required support for 48 additional hours after treatment. In all cases, revascularization was successful, and the pVAD provided adequate circulatory support. Angiography revealed that the aortic valve was not opening during balloon inflation in the target vessel (Figure 3B). Thus, the pVAD was able to capture most of the left ventricular output while providing sufficient support to prevent end-organ dysfunction. Throughout the support period, renal function remained at baseline values. None of the patients experienced neurologic complications or clinically important hemolysis. In 2 patients, however, groin hematomas developed at the arterial cannulation site. After the procedure, all patients required a blood transfusion. Four patients recovered and were discharged from the hospital. The remaining fifth patient, who was supported for 48 hours, died of heart failure and severe mitral regurgitation 10 days after withdrawal of the pVAD. He had been admitted with a non-Q-wave myocardial infarction. Because of severe left ventricular dysfunction and severe mitral regurgitation, he was deemed a very poor surgical candidate by the cardiothoracic surgeons. No other options were left, so a decision was made to intervene percutaneously. The hope was that, if left ventricular function improved after the intervention, a very high-risk mitral valve operation could be attempted. Unfortunately, left ventricular function did not improve, and the patient died of intractable heart failure on postoperative day ten.
Discussion
Because of severe comorbidities, these patients were ineligible for surgery and had no other option than high-risk PCI. Three of them had undergone previous CABG and were at high risk for complications associated with repeat surgery. Two of these 3 patients had also undergone PCI at a later time, and 1 of them subsequently had decreased left ventricular function and severe mitral regurgitation. In addition to undergoing previous CABG and concomitant aortic arch reconstruction, the third patient had a history of radiation therapy for breast cancer. Two patients had pulmonary disease severe enough to preclude surgery; 1 of these patients had severe chronic obstructive pulmonary disease with an FEV1 of 0.8 L, and the other patient had idiopathic pulmonary fibrosis. Surgery was precluded by these comorbidities and by advanced age and debilitation. Furthermore, PCI would have entailed a high risk of hemodynamic instability which would have transiently interrupted all coronary perfusion. Two cardiologists reviewed each case and deemed the patients unsuitable for surgery (Table 1). In addition, the first 4 cases were deferred by cardiothoracic surgeons because of excessively high operative risk.
Although pVAD use during PCI is intended to decrease the risk of this intervention, potential complications are associated with insertion of the pVAD itself. For instance, in patients with small or tortuous arteries or with peripheral vascular disease, insertion of the 15–17 Fr arterial cannula may be difficult. In 1 of our cases, stenting of the right and left common iliac arteries was necessary before placement of the arterial outflow cannula. Similarly, either the arterial or the venous cannula may obstruct peripheral blood flow. If this potential complication is a concern, an antegrade arterial perfusion catheter can be placed distal to the cannulation site. The transseptal approach may also be a source of complications, including left atrial rupture, creation of a clinically important residual atrial septal defect, or migration of the cannula back into the right atrium. None of these complications occurred in our series, as verified by two-dimensional echocardiography and color Doppler studies. Two patients had minimal color flow across the interatrial septum, without significant left-to-right shunting as calculated with the Qp/Qs ratio. There was no evidence of right ventricular volume overload. At 6 weeks, the color flow was no longer seen. This experience is similar to that encountered in the phase II TandemHeart trial performed by the United States Food and Drug Administration.
Our preliminary observations suggest that use of the TandemHeart pVAD may improve the morbidity and mortality rates associated with high-risk PCI. In addition, by increasing the amount of time available in which to deploy the stent safely, the pVAD may allow more accurate stent placement, thereby improving long-term vascular patency. This application may broaden the treatment options for patients at high risk for both surgical and percutaneous revascularization. Because the TandemHeart pVAD provides a higher level of circulatory support than does the intra-aortic balloon pump (IABP), the TandemHeart should also surpass the IABP with regard to this modality.6.7 Although our 20% mortality rate seems disproportionately high, only 1 of the 5 patients died, so the mortality simply reflects the small size of our series. As the technique is perfected and more experience is gained, the TandemHeart can become a workable option for very high-risk intervention which could not be undertaken at an acceptable risk with IABP support. Nevertheless, the need for careful patient selection cannot be overemphasized.
Conclusions
As noted above, these extremely high-risk patients with high jeopardy scores and difficult anatomy required prolonged balloon inflations, use of distal protection devices and rotational atherectomy. We feel that these patients could not have been treated safely with IABP-supported traditional high-risk angioplasty, using relatively undersized balloons with short inflation times for predilatation and rapid deployment of stents. The pVAD is versatile, relatively easy to insert and considerably less invasive than other ventricular assist systems. It not only provides an alternative for patients who are not surgical candidates, but it also opens the way for new therapeutic modalities in the future.
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