Sudden Cardiac Arrest Risk Is Unpredictable

Patients with congenital cardiac muscle weakness must be treated as carefully as patients with ischemic heart failure that suffered a heart attack, according to a new study.

Researchers at MedUni Vienna (Austria) studied 60 patients (median age 57 years) with dilated cardiomyopathy and a left ventricular ejection fraction (LVEF) lower than 0.5, and 30 control subjects with a LVEF of over 0.5. The study protocol included initial assessment, a second assessment after three years, and a final follow-up that included baroreceptor reflex sensitivity, short-term spectral analysis of heart rate variability, a signal-averaged electrocardiogram (ECG), and other indicators. The end points were cardiac death, resuscitated cardiac arrest, and arrhythmic death.

The results showed that cardiac death occurred in 21 patients. Resuscitated cardiac arrest and arrhythmic death caused by ventricular tachyarrhythmia (VT) was observed in 7 and 10 patients, respectively. The researchers concluded that noninvasive testing and LVEF could not reliably identify patients with dilated cardiomyopathy at risk of fatal VT, and recommended that an implantable defibrillator (ICD) be considered even in patients with mild cardiac muscle weakness. The study was published in the December 2014 issue of Circulation: Arrhythmia and Electrophysiology.

“We investigated cardiac muscle weakness patients with non-dangerous cardiac rhythm disturbances; the number of potentially fatal cases is much higher than anticipated. This difference is reflected in the risk assessment of sudden cardiac death,” said lead author Thomas Pezawas, MD, of the department of clinical cardiology. “Patients with non-ischemic heart cardiac muscle weakness are assessed with a lower risk of sudden cardiac death and therefore are less likely to receive a primary prevention ICD.”

Prophylactic ICD implantation is currently recommended in dilated, non-ischemic heart disease and LVEF of 0.30–0.35 or less. LVEF is an indicator of the heart's function which measures the volume of the beat in relation to the overall volume of blood in the left ventricle.

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