The enigma of optimal treatment for acute ventricular septal rupture

T increased use of thrombolytic therapy for acute myocardial infarction over the last 2 decades resulted in a dramatic decrease in the incidence of mechanically associated complications, such as rupture of papillary muscles, free wall, and interventricular septum.1 However, despite this encouraging upswing and improvement in surgical techniques for coronary bypass, acute interventricular septal rupture (ventricular septal defect [VSD]) remains a grave condition with a high likelihood of clinical catastrophe. The structural integrity of the interventricular septum is crucial not only for partitioning, but also for providing mechanical support for both ventricles.2 The interventricular septum actively participates in systolic contraction and diastolic relaxation and contains important elements of the conduction system.3,4 Therefore, a series of pathologic processes take place consisting of septal infarction, then macrophage-induced necrotic tissue removal, and progressive thinning of the septum, which subsequently leads to tear and rupture with the resultant shunt. Two morphologic types of acute septal rupture are recognized: simple (direct, through-and-through perforation) and complex (perforation tract ascribing a serpiginous course and dissecting into remote septal regions).5–7 The severe distortion of cardiac structure, physiology, and function caused by the sudden formation of a septal perforation exerts deleterious effects on ischemic and nonischemic septal tissues alike, and on the adjacent ventricles, valves, and the lungs. The size of the precipitating myocardial infarction, the formation of an associated ventricular aneurysm, the coexistence of right ventricular infarction, and the degree of damage to the papillary muscles each further contribute to adverse effects on a patient’s hemodynamics.8 In this issue of The American Journal of Cardiology, Thiele and colleagues9 describe a well-documented series of 23 patients with acute VSD who underwent insertion of an intraaortic balloon pump (IABP). The rationale for studying the yield of an IABP in this clinical scenario is based on the recognition that at the time of diagnosis, hemodynamic status is a major determinant of survival.10 Conceivably, improved hemodynamics with an IABP could increase survival rates. The mechanisms contributing to a potential beneficial outcome of IABP counterpulsation include lowering of the left ventricular afterload, increasing anterograde left ventricular ejection volume, and a decrease in left to right shunt. An initial reading of the report by Thiele and colleagues9 may lead to an impression that the investigators have ascertained the role of IABPs in the management of acute VSD. They found a statistically significant decrease in left-to-right shunt volume and a concomitant decrease in the magnitude of the left-toright shunt ratio with an IABP. The cardiac index increased and improvements in metabolic acidosis and serum lactate levels were documented. The investigators noted that the hemodynamic benefits were sustained over time without complications. An intriguing finding indicated that referral of 6 patients who could not be stabilized with the IABP and underwent “early” surgical closure of the VSD resulted in an ominously high mortality rate of 83%. Interestingly, an almost identical surgical mortality rate (85%) was recorded in another series of 13 similar patients who received an IABP.7 Fourteen other patients in Thiele et al’s9 report, most of whom were not in cardiogenic shock, were stable on the IABP and received a “delayed” operation. The mortality rate in this group was considerably less at 29%. Should these findings prompt a change in the current American College of Cardiology/American Heart Association guidelines,11 which recommend urgent operation for acute VSD regardless of hemodynamic status? The answer is negative for several reasons. First, unlike outcomes of other mechanical complications of myocardial infarction, the clinical outcome of patients with acute VSD does not depend on left ventricular function.12 Furthermore, the volume of left-to-right shunt through the septal perforation, either by itself or in conjunction with left ventricular ejection fraction, does not relate to clinical outcome.8,13 Second, it is well documented that in such patients, urgent operation may be a life-saving option but is clearly a high risk. Most authorities agree that these patients cannot be safely deferred to an elective operation to improve risk.14 Thiele et al’s9 data reveal a disappointing 56% overall mortality rate. The investigators’ experience denotes that mortality remains high regardless of the infarct location (50% for anterior infarction vs 54% for inferior infarction). The presence or absence of cardiogenic shock in relation to the infarct location was associated with high mortality as well (50% vs 50% for anterior infarction, respectively and 54% vs 46% for inferior infarction, respectively). The study’s design failed to identify the select patients who stand to gain a real benefit from a combined strategy of From the Division of Cardiology, McGuire Veterans Affairs Medical Center, Medical College of Virginia Hospitals, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia. Manuscript received April 29, 2003; revised manuscript received and accepted May 12, 2003. Address for reprints: On Topaz, MD, Division of Cardiology, McGuire Veterans Affairs Medical Center, 1201 Broad Rock Boulevard, Richmond, Virginia 23249. E-mail: ontopaz@aol.com.