Cardiac NewsLine is a newsletter that updates medical professionals in the most recent advances in cardiac care at NYU Langone Medical Center. This edition's topics include:

• The Expanding Role of Minimally Invasive Cardiac Surgery
• Recent Advances in Electrophysiology - New Treatment for Heart Failure
• Optimizing the Design of Stents

The Expanding Role of Minimally Invasive Cardiac Surgery

Aubrey C Galloway, MD, Professor of Surgery; Greg H Ribakove, MD, Associate Professor of Clinical Surgery; Eugene A Grossi, MD, Associate Professor of Surgery; and Stephen B. Colvin, MD, Chief, Division of Cardiothoracic Surgery

The NYU Langone Medical Center Division of Cardiothoracic Surgery began research in less invasive forms of cardiac surgery in 1994 and introduced the Port Access approach for mitral valve and coronary surgery in an FDA-sponsored trial in 1996. Since that time the use of minimally invasive cardiac surgery has expanded dramatically, and NYU surgeons now have experience in 1196 patients using these techniques (see table below).

A review of this experience reveals several trends. First, in the treatment of coronary artery disease, several less invasive forms of surgery have become available and are used in selected populations. Techniques include (1) minimally invasive direct coronary artery bypass (MIDCAB), which is performed through a mini-thoracotomy incision without cardiopulmonary bypass, (2) off-pump coronary artery bypass (OPCAB), which is performed through a sternotomy incision without cardiopulmonary bypass, and (3) Port Access (PACABG), which uses a balloon catheter system to perfuse the patient and protect the heart, allowing multi-vessel bypass (and valve surgery) through a mini-thoracotomy incision.

Advantages of the Minimally Invasive Approach

Each technique has its advantages. In a comparative trial between Port Access and conventional surgery for multi-vessel coronary bypass, Port Access patients had less pain, had less systemic stress response, and recovered in approximately one-half the time, based on the Duke activity index score. Similarly, important advantages were seen in patients having either form of off-pump surgery (OPCAB and MIDCAB). Since these techniques avoid cardiopulmonary bypass, the risk of stroke and other bypass-related complications is diminished. An NYU comparison in high-risk patients who have atheromatous disease of the aortic arch and required coronary bypass demonstrated that patients who received OPCAB or MIDCAB had one-half the risk of stroke and death compared to those who had conventional surgery. Currently at NYU approximately 25-30% of patients requiring CABG receive a less invasive alternative operative approach, either Port Access, MIDCAB, or OPCAB. This strategy, which allows "risk stratification" based on anatomy and risk factors such as severe vascular disease or renal failure, has led to improved overall results and a lower risk.

Minimally Invasive Valve Surgery

Even more striking than the results with coronary bypass surgery has been the impact of minimally invasive approaches on valvular surgery. The minimally invasive approach has become the standard of care for most patients requiring isolated valve repair or replacement, with the Port Access approach used for virtually all mitral valve surgery. Results have been excellent (see table below) with an extremely low operative risk, less bleeding, less risk of infection, and shorter overall recovery. Follow-up studies have shown that valve repair durability is equivalent to that achieved with conventional surgery. Thus, the shortterm risks are reduced with equivalent long-term results.

Summary

The large and extremely favorable NYU Langone Medical Center experience with minimally invasive cardiac surgery suggests that this less traumatic form of surgery is now preferred for most patients requiring aortic or mitral valve surgery, for ASD repair and for atrial myxoma excision. Patients requiring coronary artery bypass are riskstratified using either conventional surgery, Port Access, MIDCAB or OPCAB, an approach which has lowered the overall risk significantly. Patients having minimally invasive cardiac surgery require less blood, have fewer infections and recover more quickly. These emerging new technologies are having a dramatic impact on patient care, lowering the overall morbidity, pain and suffering associated with heart surgery. Further improvements, ranging from robotics to gene therapy, hold promise for future breakthroughs.

Recent Advances in Electrophysiology - New Treatment for Heart Failure

By Larry Chinitz, MD, Director, Electrophysiology Laboratory; Neil Bernstein, MD, Assistant Professor of Medicine; and Douglas Holmes, MD, Assistant Professor of Medicine

Biventricular pacing results in resynchronization of left ventricular contraction and is now a treatment option for patients with heart failure. Studies in Europe have demonstrated that patients with symptomatic heart failure can achieve significant functional improvement when they are simultaneously paced from right and left ventricles. This treatment is now being investigated in appropriate patients in the United States. While heart failure is associated with delayed and asymmetric left ventricular contractility, multi-site pacing has been shown to significantly improve hemodynamics. The Division of Clinical Cardiac Electrophysiology at NYU is actively enrolling patients in a number of new studies to expand and define the indications of this therapy. We anticipate that this will make a substantial impact on the enormous morbidity and mortality in patients with heart failure. The following clinical trials are available:

VECTOR: Designed for patients without standard pacing indications, biventricular pacing can be recommended if their baseline QRS is greater than 135 ms and they have class II or greater heart failure.

MIRACLE ICD: This protocol is for patients with standard indications for ICD implantation and baseline QRS duration greater than 130 ms. Preliminary clinical data suggest that such pacing can result in fewer ICD discharges and improved heart failure status.

PAVE (Pacing after AV node ablation): Since right ventricular pacing can compromise hemodynamic function in patients with normal left ventricular function, biventricular pacing will be compared to RV pacing after AV node ablation.

New Diagnostics for Sudden Death T-wave Alternans (TWA) is a powerful new tool for risk, stratifying patients for sudden death. This test examines the beat-tobeat variation of cardiac repolarization and is emerging as an accurate predictor of ventricular arrhythmias. Patients with past myocardial infarction, reduced ejection fraction, and non-sustained ventricular tachycardia on routine screening Holter recordings are the focus of the ABCD trial (Alternans before card overter defibrillator). Such patients have shown better survival with ICD therapy if they demonstrated inducible VT during EPS. This study will determine whether people with normal EPS results but abnormal TWA findings will also benefit from ICD placement. Increasing our ability to select and protect patients from sudden death is the major focus of cardiac electrophysiologists and the goal of this prospective study.

In summary, NYU Langone Medical Center is taking an aggressive approach to the management and risk stratification of patients with impaired left ventricular function and heart failure. We believe that this approach is justified by the enormous mortality in this population and the number of patients at risk.

Optimizing the Design of Stents

Norma Keller, MD, Assistant Clinical Professor of Medicine

Stents have revolutionized the world of interventional cardiology, particularly in regard to acute occlusion and restenosis. A major challenge was defining the role of stents in the setting of acute myocardial infarction (AMI). The Stent-PAMI (Randomized Trial of Primary PTCA versus heparin-coated stent implantation during acute myocardial infarction) trial compared percutaneous transluminal coronary angioplasty (PTCA) to stenting; and the CADILLAC (a randomized comparison of the ACS Multilink coronary stent system with or without abciximab versus PTCA with or without abciximab in the treatment of patients with acute myocardial infarction) trial, evaluated the administration of abciximab with primary PTCA or stenting during AMI. Prior to our participation in these studies, direct PTCA was the therapeutic strategy of choice at NYU Medical Center. We now still perform emergent cardiac catheterization for patients presenting with AMI, but then proceed with primary PCI (Percutaneous Coronary Intervention) and utilize stenting if feasible.

Since the introduction of coronary stents, there has been a movement to design newer and better stents. The BiodivYsio stent is a novel stent that is coated with phosphorylcholine. This biological coating appears to mimic the main lipid headgroup component of the natural cell membrane producing a nonactivating biological interface. This was designed to improve the biocompatibility of stents. We were honored to have been selected as a site in the recently completed randomized international multicenter trial, Biocompatibles BiodivYsio Stent in Randomized Control Trial (DISTINCT), which compared this stent to the commercially available Duet stent. Although the BiodivYsio stents are not commercially available in the United States, we are fortunate to be one of 10 centers in the United States to participate in a Registry evaluating the 11 and 15 mm BiodivYsio stent in patients with symptomatic coronary artery disease due to de novo lesions.