ASSOCIATION BETWEEN REDUCED HEART-RATE-VARIABILITY AND LEFT-VENTRICULAR DILATATION IN PATIENTS WITH A FIRST ANTERIOR MYOCARDIAL-INFARCTION

Background-Reduced heart rate variability has been identified as an important prognostic factor after myocardial infarction. This factor is thought to reflect an imbalance between sympathetic and parasympathetic activity, which may lead to unfavourable loading conditions and thus promote left ventricular dilatation. Patients and methods-298 patients in a multicentre clinical trial were randomised to captopril or placebo after a first anterior myocardial infarction. All patients were treated with streptokinase before randomisation. In the present substudy full data including heart rate variability and echocardiographic measurements were available from 80 patients. Patients were divided into two groups: those with a reduced (less than or equal to 25) heart rate variability index and those with normal heart rate variability index (> 25). Heart rate variability was evaluated by 24 h Holter monitoring before discharge. Left ventricular volumes were assessed by echocardiography before discharge and three and 12 months after myocardial infarction. Extent of myocardial injury, severity of coronary artery disease, functional class, haemodynamic variables, and medication were also considered as possible determinants of left ventricular dilatation. Results-Before discharge end systolic and end diastolic volumes were not different in the two groups. After 12 months in patients with a reduced heart rate variability, end systolic volume (mean (SD)) had increased by 6 (14) ml/m(2) (P = 0.043) and end diastolic volume had increased by 8 (17) ml/m(2) (P = 0.024). Left ventricular volumes were unchanged in patients with a normal heart rate variability. Also, patients with left ventricular dilatation had a larger enzymatic infarct size and higher heart rates and rate-pressure products. A reduced heart rate variability index before discharge was an independent risk factor for left ventricular dilatation during follow up. Measurement of heart rate variability after three months had no predictive value for this event. Conclusion-Assessment of the heart rate variability index before discharge, but not at three months, gave important additional information for identifying patients at risk of left ventricular dilatation

ASSOCIATION OF LEFT-VENTRICULAR REMODELING AND NONUNIFORM ELECTRICAL RECOVERY EXPRESSED BY NONDIPOLAR QRST INTEGRAL MAP PATTERNS IN SURVIVORS OF A FIRST ANTERIOR MYOCARDIAL-INFARCTION

Background Progressive left ventricular dilatation after myocardial infarction is associated with a high mortality rate, the majority of which is arrhythmogenic in origin. The underlying mechanism of this relation remains unknown. It has been suggested, however, that left ventricular dilatation is accompanied by changes in repolarization characteristics that may facilitate the occurrence of life-threatening ventricular arrhythmias. Methods and Results We examined 62-lead body surface QRST integral maps during sinus rhythm in 78 patients at 349+/-141 days after thrombolysis for a first anterior myocardial infarction. Visual map analysis was directed at discriminating dipolar (uniform repolarization) from nondipolar (nonuniform repolarization) patterns. In addition, the nondipolar content of each map was assessed quantitatively with the use of eigenvector analysis. Nondipolar map patterns were present in almost one third of the patients (32%). Left ventricular end-systolic and end-diastolic volumes were assessed echocardiographically before discharge and after 3 and 12 months with the use of the modified biplane Simpson rule. The increase in left ventricular end-systolic volume 1 year after myocardial infarction was more pronounced in patients with nondipolar QRST integral map patterns (14.47+/-14.10 versus 4.22+/-8.44 mL/m(2), P=.017). In patients with an increase in end-systolic volume of more than 16 mL/m(2) (upper quartile), the prevalence of nondipolar maps was 89% compared with 29% in patients with dilatation of less than 16 mL/m(2). In addition, the nondipolar content of maps in patients in the upper quartile was significantly increased compared with the lower quartiles (49+/-14% versus 37+/-12%, P=.013). Logistic regression analysis revealed that an end-systolic volume of more than 42 mL/m(2) after 1 year contributed independently to the appearance of nondipolar maps. Patients with high-grade ventricular arrhythmias showed a higher nondipolar content (49+/-17% versus 39+/-10%, P=.013). QT(c) dispersion did not discriminate between patients with and those without high-grade ventricular arrhythmias. Also, the association between left ventricular remodeling and nondipolar map patterns was confirmed prospectively in an additional group of 15 patients. Conclusions Nondipolar map patterns are present in 32% of patients after thrombolysis for a first anterior myocardial infarction and are associated with increased left ventricular dilatation. These data support the hypothesis that left ventricular dilatation after myocardial infarction lends to changes in repolarization characteristics that may facilitate the occurrence of life-threatening ventricular arrhythmias