Objectives. The goal of this study was to evaluate clinical and autonomic variables (heart rate variability and baroreflex sensitivity) related to hemodynamic tolerability of VT in patients with sustained monomorphic VT and a healed myocardial infarction. Background. Sustained ventricular tachycardia (VT) with hemodynamic deterioration is associated with a worse prognosis than that of well tolerated VT. The causes of hemodynamic deterioration of VT are incompletely understood. Methods. Twenty-four consecutive patients with sustained monomorphic VT and a healed myocardial infarction (mean age ± SD 66 ± 8 years, left ventricular [LV] ejection fraction 37 ± 11%) were assigned to group 1 if the VT was well tolerated (n = 11) or to group 2 if faintness or syncope occurred or if systolic blood pressure was <90 mm Hg with clinical signs of shock (n = 13). Results. No difference was found between the two groups in age, LV function, rate and duration of the VT or heart rate variability. However, patients in group 2 had a significantly lower baroreflex sensitivity (3.4 ± 1.1 vs. 7.1 ± 3.7 ms/mm Hg, p = 0.003). Multiple logistic regression analysis showed that only the value of baroreflex sensitivity (p = 0.0003) - but not age, LV ejection fraction, VT cycle length or SD of the RR interval (all p > 0.25) - correlated with the tolerability of the VT. Finally, LV ejection fraction (p = 0.0001) and baroreflex sensitivity (p = 0.0003) - but not age, cycle length of the tachycardia or SD of the RR interval - predicted cardiac death or unstable VT during follow-up. Conclusions. These data suggest that an impaired cardiovascular reflex response may play a key role in the hemodynamic deterioration of sustained VT and that the evaluation of baroreflex sensitivity in patients at high risk for sustained VT may become useful both in risk stratification and in the individualization of treatment.
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