Incidence and correlates of complex ventricular arrhythmias during dobutamine stress echocardiography after acute myocardial infarction.

Although previous studies have confirmed the safety of dobutamine stress echocardiography, complex ventricular arrhythmias have been reported. Our aim was (1) to identify the markers of increased arrhythmic risk during dobutamine stress echocardiography and (2) to assess whether the occurrence of major ventricular arrhythmias during the test may represent a clinically useful marker of electrical instability. Three hundred and seventy-seven consecutive survivors from acute myocardial infarction, off cardioactive therapy, underwent dobutamine stress echocardiography 11.4 days after the acute event. Holter monitoring with assessment of heart rate variability and echocardiographic determination of left ventricular ejection fraction. In addition, exercise stress testing, signal averaged ECG and coronary angiography were carried out, respectively, in 357, 150 and 273 patients. Ten subjects showed complex ventricular arrhythmias (eight non-sustained and one sustained ventricular tachycardia and one ventricular fibrillation) during dobutamine stress echocardiography (group A), whilst 366 did not (group B). Complex ventricular arrhythmias were detected by Holter monitoring in 8/10 patients in group A and 45/367 patients in group B (odds ratio 28.6, 95% CI 5.4-92.2) and by exercise testing in 4/10 patients in group A and 33/347 patients in group B (odds ratio 6.3, 95% CI 1.4-27.2). Ejection fraction < 40% was present in 3/10 patients in group A and 50/367 in group B (odds ratio 2.7, 95% CI 0.3-12.2), whilst multivessel disease was present, respectively, in 8/10 and 176/263 patients (odds ratio 1.9, 95% CI 0.3-25.5). Reduced heart rate variability and the presence of late potentials on signal averaged ECG were found in, respectively, 40/367 and 13/140 patients in group B, but none were found in group A. A total of 61 events (35 CABG, 15 PTCA, four cardiac deaths and seven non-fatal reinfarctions) occurred during the follow-up (11.4 months, range 6 to 20): four in group A and 57 in group B. No documented major arrhythmic event was reported. We conclude that (1) complex arrhythmias during dobutamine stress may occur in patients early after acute myocardial infarction; (2) the preexisting evidence of frequent, as well as repetitive, arrhythmias represents a potential marker of increased risk in this connection and, finally, (3) dobutamine-induced arrhythmias seem to represent an uncommon, even though potentially dangerous, event but not a useful new "window' on electrical instability of post-MI patients.

[Late ventricular potentials in the post-infarct patient. A follow-up at 4 years]. / I potenziali tardivi ventricolari nel post-infarto. Follow-up a 4 anni.

We performed a prospective study to evaluate the prognostic significance and the natural history of late ventricular potentials (LPs) in 209 patients (165 males and 44 females; mean age 59.8 +/- 10 years) who survived acute myocardial infarction. Signal-averaged electrocardiograms (SA-ECGs) were performed before hospital discharge (16 +/- 5 days) and after four years (mean follow-up 42 +/- 7 months). SA-ECGs were processed using a 40 Hz high-pass bidirectional filter. Duration of "filtered" QRS (normal value < 120 msec), duration of the low-amplitude signals (n.v. < 39 msec) and last 40 msec voltage of the QRS complex (n.v. > 20 microV) were measured. LPs were defined as the presence of two or more abnormal values. In addition, 24-hour Holter monitoring was performed in all patients, and left ventricular ejection fraction (LVEF) was determined by scintigraphy in 120 (57.4%). Sixty patients (28.7%) had LPs before hospital discharge (group 1), and 149 (71.3%) had normal SA-ECGs (group 2). During the follow-up period there were 10 arrhythmic events, 7 of which were sudden deaths, and three cases of sustained ventricular tachycardia. SA-ECG was repeated in 141 patients (68%). The mean values of SA-ECG's parameters did not change significantly between the two controls, and the correlation was good for all of them. Despite this, spontaneous normalization of SA-ECGs occurred in 21 patients (60%) and the subsequent appearance of LPs was seen in 13 (12%); in these latter, the SA-ECG's parameters measured before hospital discharge were "borderline" and significantly different from those who did not change. The sensitivity of SA-ECG as a predictor of arrhythmic events was 80% and the specificity 74%. Patients with arrhythmic events had a longer filtered QRS (126 +/- 33 vs 103 +/- 12 msec; p < 0.001), longer duration of the low-amplitude signals (57 +/- 23 vs 32 +/- 11 msec; p < 0.001), lower voltages (17 +/- 8 vs 36 +/- 24 microV; p < 0.001), and, moreover, higher peak CK values, lower LVEF and higher value of Lown modified class. In conclusion, SA-ECG confirms its value in identifying patients at risk of arrhythmic events after myocardial infarction. SA-ECG recordings taken before the discharge can be used to predict serial changes during follow-up.

Clinical correlation between diabetic and non diabetic patients with myocardial infarction.

We have studied 130 patients with diabetes mellitus and 455 patients without. All the patients were consecutively admitted to our Coronary Care Unit with their first myocardial infarction. We have observed a higher incidence of heart failure, in-hospital mortality, atrial fibrillation, conduction abnormalities, and post-infarction angina among diabetics. Nevertheless, diabetic patients do not show evidence of larger infarcts than those without diabetes. In our patients the higher mortality among diabetics is related to an increased occurrence of left ventricular failure. Moreover, post-infarction ischemic episodes are more common compared with non diabetics. Since infarcts in diabetics do not seem to be more extensive than in non diabetics, we suggest, in accordance with others, that the poorer outcome among diabetic patients with AMI could be related to an underlying cardiac dysfunction of diabetics in addition to coronary artery diseases.

Prognostic significance and evolution of late ventricular potentials in the first year after myocardial infarction: a prospective study.

We performed a prospective study of the high-frequency components of the terminal portion of the QRS complex in 220 patients who survived acute myocardial infarction. Signal-averaged electrocardiograms (SA-ECGs) were performed before hospital discharge (16 +/- 6 days) and then serially at regular intervals over the following year. SA-ECGs were processed using a 40 Hz high-pass bidirectional filter. Duration of "filtered" QRS (D-normal value less than 120 ms), duration of the low-amplitude signals (D40 - n.v. less than 39 ms) and last 40 ms voltage of the QRS complex (V40 - n.v. greater than 20 microV) were measured. Late potentials (LPs) were defined as the presence of two or more abnormal values. In addition, 24-hour Holter monitoring was performed in 208 patients and left ventricular ejection fraction (LVEF) was determined by scintigraphy in 111. Sixty-two patients (group 1) had LPs, 158 had normal SA-ECGs (group 2). Spontaneous normalization of SA-ECGs occurred in 20% of patients after 6 months, although the mean values of D, D40 and V40 did not change significantly and the reproducibility was very good for all the indexes during all the follow-up controls. Three patients had sudden death and three presented again with spontaneous, sustained ventricular tachycardia. Five of 62 (8%) group 1 patients had an arrhythmic event compared with one of 158 patients (0.6%) in group 2. The sensitivity of SA-ECGs as a predictor of arrhythmic events was 83% with a specificity of 73%. Patients with subsequent arrhythmic events had longer filtered QRS (133 +/- 19 vs 104 +/- 16 ms; P less than 0.001), longer duration of the low-amplitude signals (54 +/- 15 vs 33 +/- 14 ms; P less than 0.01), and lower voltages in the last 40 ms of the filtered QRS (11 +/- 3 vs 36 +/- 25 microV; P less than 0.02) and, moreover, higher peak CK values and lower LVEF than those without such events. In conclusion, SA-ECGs provide important prognostic information in identifying patients at risk of arrhythmic events after myocardial infarction although dynamic changes of LPs are observed during the first year after myocardial infarction.

[Sinus node electric activity in prolonged atrial pauses in subjects with the sick sinus syndrome]. / Attivitá elettrica sinusale durante pause atriali "prolungate" in soggetti con malattia del nodo del seno.

Sinus node electrogram (SNE) was recorded in 15 patients with sick sinus syndrome (SSS) in which prolonged atrial pauses were observed. The aim of this study was clarify the physiopathological mechanisms underlying atrial pauses as well as to evaluate the sensitivity of sinoatrial conduction time (SACT) directly measured on SNE and of SACT estimated with the indirect Strauss method with respect to the detection of SSS. The following results were obtained: Sinus electrical activity was recorded during atrial pauses (greater than or equal to 2 basic sinus cycle length) in all the 9 patients in which the pauses spontaneously occurred and in the 2 patients in whom the pauses of 2860 and 3190 msec were induced by atrial pacing. In one of these latter two patients, moreover, a complete electrical desynchronization was observed. In the remaining 4 patients in whom, pauses (greater than or equal to 3 sec) were induced by carotid sinus massage of in 3 no sinus electrical activity was detected on SNE while in 1 advanced sinus node desynchronization was observed. Direct sinoatrial conduction time was abnormally prolonged in 6 patients with SSS and indirect sinoatrial conduction time in 9 patients.

Mexiletine action on the specialized tissues of the human heart.

Electrophysiological properties of mexiletine (3 mg/kg i.v.) were studied in fifteen patients with various degrees of abnormalities in the specialized conduction system. Sinus cycle length was decreased in all patients; sinus node recovery time was increased in all patients, but the increment was not statistically significant. Atrial and atrioventricular (AV) nodal refractoriness were not modified. The relative refractory period of the His-Purkinje system was reduced in patients with normal intraventricular conduction on the surface electrocardiogram; no changes were noted in five patients with intraventricular conduction delay. In two patients, in whom AV nodal refractory period curves showed antegrade dual AV nodal pathways, mexiletine increased refractoriness of the fast pathway. This report points out that the drug is effective against arrhythmias sustained by a reentry mechanism, not only in the ventricles, but also in the AV node.

[The sinus node electrogram in the evaluation of atrial pauses]. / L'elettrogramma del nodo del seno nella valutazione delle pause atriali.

The aim of this study was to establish the electrophysiological mechanism of atrial pauses, defined as a sudden lengthening of atrial cycle greater than or equal to 10% of its basal value. The sinus node electrogram (SNE) was recorded during electrophysiological study in 20 subjects. Satisfactory recordings of 64 pauses were obtained, 25 of which were spontaneous, 16 were induced by short periods of atrial pacing (AP) in normal subjects, whereas 23 atrial pauses were induced with the premature stimulation method. The basal sinus cycle and the one during the spontaneous pauses were measured from the upstroke slope on the SNE. The electrically induced pauses of the sinus cycle were measured from the artifact of the stimulus to the upstroke slope of the SNE of the first post-pacing beat. We have found that: 1-spontaneous atrial pauses correspond to a moderate slowing of the sinus cycle and to a depression of the sinoatrial conduction occasionally up to a second degree sinoatrial block. Only in subjects with sick sinus disease, the atrial pauses are induced by depression of the sinus automatism; 2-in normal subjects the AP results in a sinoatrial conduction delay; 3-the single extrastimulus regularly produces a moderate increase of the sinoatrial conduction time with variable but minimal effects on the sinus node automatism.

[Activity of a new long-acting anti-arrhythmic drug on ventricular extrasystole. Study with Holter continuous electrocardiographic monitoring]. / Attività di un nuovo antiaritmico "long-acting" sull'extrasistolia ventricolare. Studio con il monitoraggio elettrocardiografico continuo di Holter.

Therapeutic effectiveness of a new long-acting antiarrhythmic preparation was evaluated in 31 patients with sustained premature ventricular beats. After an observation period, a 24 hours Holter monitoring was performed. A group (21 patients) was treated with dihydrochinidine 250 mg twice a day; another group (11 patients) was treated with 500 mg twice a day. In the latter group was determined basal chinidinemia on the first and third day. A 24 hours Holter monitoring was repeated on the fourth day. In the first group we reached a 77.4% reduction of the arrhythmia: not enough, however, to agree with established statements. We reached a larger reduction (84.7%) with higher doses (1000 mg daily). This drug was well tolerated in both groups.