| Abstract: | This study was undertaken to test the validity of methods of evaluating ventricular tachycardia and in therapeutic surveillance. One hundred and thirty nine patients aged 16 to 84 years, with and without severe ventricular arrhythmias (ventricular tachycardia, VT, and fibrillation, VF) were divided into two groups after clinical, echocardiographic and 24 hour Holter investigations: Group I comprised 26 patients with a least one documented attack of VT or VF; Group II comprised 113 patients without these arrhythmias, who complained of dizziness, syncope, and/or their ECG showed a conduction defect, and so electrophysiological investigation was undertaken. A protocol of ventricular stimulation was undertaken in addition to the usual measurements of conduction times, comprising incremental ventricular stimulation from 100 to 200/min, single and paired extrastimulus in sinus rhythm and during ventricular pacing at rates of 100 and 150/min, the first extrastimulus being programmed 10 ms after the end of the ventricular effective refractory period. Excluding bundle to bundle reentry, the following results were obtained: In Group I: VT was triggered 16 times (61,5 p. 100), and in 4 of these cases VF occurred and required defibrillation. Ten patients had previous myocardial infarction; 5 patients had left ventricular dilatation. In 2 cases runs of 3 or 4 VES were recorded. No arrhythmia could be induced in 8 cases (30,8 p. 100); 5 of these patients had apparently normal hearts. In Group II: VT (greater than 5 VES) was triggered in 22 cases (19,5 p. 100) and in 4 cases this degenerated to VF requiring defibrillation. 11 patients had apparently normal hearts; 6 patients had left ventricular dilatation and 4 patients had previous myocardial infarction. 1 to 4 repetitive VES were observed in 67 cases (59,3 p. 100): the heart was judged to be normal in all patients except those with previous infarction. No correlation was established between the ability to induce VT and age, syncope, or ECG changes (especially bundle branch block). However, a correlation was found between the induction of VT and underlying cardiac disease and the method of induction of VT; in Group II, all episodes of VT were triggered by delivering paired ventricular extrastimuli on a background paced rhythm. These results show that repetitive ventricular responses can easily be triggered and that this has no pathological significance.(ABSTRACT TRUNCATED AT 400 WORDS) |
