Low Ejection Fraction and Extensive Scar Tissue Predict Recurrent Ventricular Arrhythmias or Death in Cardiac Arrest Survivors

December 12, 2003

December 12, 2003    A recent study showed that extensive scar tissue and severely depressed left ventricular ejection fraction (LVEF) are independent predictors of death or recurrent ventricular arrhythmias in coronary artery disease (CAD) patients with aborted sudden death. Published in Circulation, researchers from Leiden University Medical Center (Leiden, The Netherlands) also suggested that their findings correlate the presence of ischemia or viable myocardium with a higher incidence of ventricular arrhythmia recurrences, and recommend revascularization to avoid events. [1]

Given the identified predictive value of LVEF and extensive scar tissue, as well as the suggested benefit of revascularization, use of single photon emission computed tomography (SPECT) imaging that enables clinicians to assess ischemia, viability, scar tissue, and LVEF may help in stratifying patients at risk. However, the authors cautioned that "randomized (to treatment) trials are needed to draw definitive conclusions concerning this issue."

As noted in prior studies, ischemia and large areas of scar tissue are presumed responsible for triggering ventricular arrhythmias and subsequent revascularization may increase electrical stability, thereby reducing the risk of arrhythmic death. The present study was conducted to study the relationship between ischemia, viability, scar tissue, and revascularization and its impact on the incidence of ventricular arrhythmias.

Jeopardized myocardium defined as ischemic/viable tissue on scintigraphy

The study included 156 consecutive patients (mean age, 63 ± 10 years; 132 males) with significant CAD (>= 50% diameter stenosis) who survived cardiac death attributable to ventricular arrhythmias. Ventricular fibrillation was the presenting arrhythmia in 84 patients (54%), ventricular tachycardia, in 72 patients (46%). Mean LVEF was 40 ± 19%.

All patients were assessed by stress-rest perfusion scintigraphy. Seventy-three patients (47%) had jeopardized myocardium, defined as the presence of ischemia/viable tissue, and 44 patients (60%) underwent subsequent revascularization (coronary artery bypass graft surgery, 61%; percutaneous transluminal coronary angioplasty, 39%). Final antiarrhythmic therapy, based on the outcome of electrophysiological testing or LVEF, included implantable cardioverter defibrillator (ICD) implantation (72%), radiofrequency catheter ablation (13%), or antiarrhythmic medication (52%) (in some cases, patients received more than one therapy).

Majority of deaths caused by ongoing heart failure; ICDs still encouraged

During median follow-up of 26 months, 15 patients (10%) died; cardiac death occurred in 11 patients (7%). Ten of the 11 cardiac deaths (91%) were caused by ongoing heart failure, and 1 death was the result of sudden cardiac death. Forty-two patients (27%) experienced recurrence of ventricular arrhythmia.

Of interest, the authors noted that 36 of the 42 patients (86%) experiencing recurrence had undergone ICD implantation and suggested that the number of sudden cardiac deaths may have been higher if patients had not received ICD therapy.

"Previous studies focusing on ischemia, viability, scar tissue, and long-term survival were not capable of distinguishing between these modes of deaths, but because of the presence of the ICD, the present study is the first to provide information on mode of death in these patients," the authors wrote in support of ICD implantation for high-risk patients.

Which is responsible for recurrences: jeopardized myocardium or scar tissue?

In evaluating the benefit of revascularization, the authors considered patients with ischemia and viable myocardium as having jeopardized myocardium. Patients with jeopardized myocardium had lower event rates than patients without jeopardized myocardium. However, patients with jeopardized myocardium who underwent revascularization had a 13% event rate, whereas those with jeopardized myocardium treated medically had a 38% event rate, findings that "confirm the suggestion that revascularization of jeopardized myocardium is needed to avoid events," according to the authors.

Patients with events more often exhibited LVEF <= 30%, more extensive scar tissue, and less ischemic/viable myocardium -- and had less frequent revascularization -- than did patients without events. But the authors pointed out that on multivariate analysis, only extensive scar tissue and LVEF <= 30% were identified as predictors of outcome in survivors of aborted sudden death.

The next step in treatment is...

Study limitations, according to the authors, include the fact that the present study was not a prospective one and that it lacked randomization to treatment (medical therapy vs revascularization). Viability assessment with technetium-99m tetrofosmin may have underestimated the presence of viable tissue. Finally, viability and ischemia were grouped as jeopardized myocardium, and elevated creatine kinase-MB levels in 5% of patients at the index event may have influenced study results.

The authors stressed the importance of scintigraphic evaluation of patients with CAD and aborted sudden death and suggested that "in the presence of jeopardized myocardium, an attempt at revascularization should be made." Because of the higher rate of mortality attributable to heart failure, the authors believe that the next step in treating such patients should focus on therapeutic options for heart failure.

Reference
  1. Borger van der Burg AE, Bax JJ, Boersma E, Pauwels EKJ, van der Wall EE, Schalij MJ. Impact of viability, ischemia, scar tissue, and revascularization on outcome after aborted sudden death. Circulation. 2003;108:1954-1959.

By Staff Writer, Medscape CRM
Reviewer: Albert A. Del Negro, MD

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