Once daily felodipine in preventing ergonovine-induced myocardial ischaemia in Prinzmetal's variant angina.

The efficacy of extended-release felodipine in preventing ergonovine-induced myocardial ischaemia was assessed in 14 patients (12 male, two female, aged 56 +/- 7 years) with Prinzmetal's variant angina. Four of the patients had normal coronary arteries, eight had one-vessel and two had two-vessel disease. The ergonovine test was performed once in basal conditions and twice 5 days after beginning the oral administration of felodipine 20 mg o.d., 4 and 24 h after the last administration. During a continuous 6-lead ECG recording, ergonovine was injected at doses of 25, 50, 100, 200, and 400 micrograms at 5 min intervals. Blood samples for felodipine plasma concentrations were drawn at the time of the tests. The basal ergonovine test was positive in all 14 patients (seven with anterior and seven with inferior ST segment elevation > 0.1 mV) at a mean ergonovine dose of 162 +/- 138 micrograms. The test was repeated 4 h after the last felodipine administration and was negative in 13 patients (93%), but 24 h after the last drug administration, eight patients (57%) had a positive test response (five with anterior, three with inferior ST segment elevation) at a higher ergonovine dose than at baseline (150 vs 97 micrograms, P = 0.042). The only differences between patients with a negative and a positive test were the mean values of the left ventricular end-diastolic pressure (9.3 vs 14.9 mmHg, P = 0.002) and the ergonovine doses used in the baseline tests (250 vs 97 micrograms, P = 0.034).(ABSTRACT TRUNCATED AT 250 WORDS)

[The behavior of late potentials in myocardial infarct patients undergoing myocardial revascularization]. / Comportamento dei potenziali tardivi in pazienti con infarto miocardico sottoposti a rivascolarizzazione miocardica.

Ventricular late potentials recorded on the body surface in patients with old myocardial infarction (MI) are considered to reflect slow conduction, due to the presence in the infarct border zone of viable myocardium within scarred tissue. To assess the prevalence of late potentials in a population with old MI and no malignant arrhythmias and to verify whether myocardial revascularization may influence the substrate responsible for the occurrence of late potentials, 80 patients with old MI (75 males, 5 females), aged 55 +/- 9 years, undergoing coronary surgery, were studied. A Marquette MAC15 HiRes electrocardiogram recorder was used to identify late potentials before and after surgery. Late potentials were defined following the most accepted criteria reported in the literature. Statistical analysis was performed using logistic regression to determine the association of several clinical, hemodynamic and surgical variables with the presence of late potentials. Late potentials were present in 28 patients (35%) before surgery and disappeared in 11 (39%) after surgery. Inferior MI and female sex were the only independent predictors of the presence of preoperative late potentials. On the other hand, persistence of late potentials after surgery was related to the presence of inferior MI and left ventricle aneurysm. These data suggest that revascularization is capable of abolishing late potentials, probably due to functional recovery of perinecrotic hibernated myocardium. With particular anatomic conditions (inferior MI, aneurysm), this functional recovery seems not to be sufficient for the disappearance of late potentials.

Comparison of isoproterenol and exercise tests in asymptomatic subjects with Wolff-Parkinson-White syndrome.

In order to evaluate the effects of increases of sympathetic tone in ventricular response during atrial fibrillation and in the relationship between the accessory pathway effective refractory period (ERP) and ventricular rate during atrial fibrillation, 20 male subjects, aged 19 +/- 6 years, were studied electrophysiologically in basal conditions, after isoproterenol infusion (2-4 micrograms/min) and during submaximal bicycle exercise test, at a constant workload equal to that which increases the sinus rate to the same extent (140 beats/min) induced by isoproterenol infusion. Accessory pathway ERP was evaluated at the same driven rate (150 beats/min) in both instances. In the control study as during both tests atrial fibrillation paroxysms were induced by burst stimulation. In control conditions the rate increase from 100 to 150 beats/min induced a reduction of accessory pathway ERP from 266 +/- 27 msec to 244 +/- 22 msec (P less than 0.005). At the same driven rate of 150 beats/min, isoproterenol infusion and exercise test induced a more marked shortening of accessory pathway ERP to 211 +/- 28 msec (P less than 0.005) and to 214 +/- 29 msec (P less than 0.005), respectively. Atrial fibrillation paroxysms lasting more than 10 seconds were induced in 20/20 cases in the control study, in 15/20 during isoproterenol infusion and in 13/19 cases during exercise test. The shortest cycle length during atrial fibrillation was reduced from a basal value of 253 +/- 72 msec to 204 +/- 27 msec (P less than 0.05) during isoproterenol infusion and to 236 +/- 32 msec (NS) during exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)

Dispersion of ventricular repolarization in the long QT syndrome.

To identify markers of dispersion of the ventricular repolarization in the idiopathic long QT syndrome, body surface potential maps were analyzed in 40 such patients (mean age +/- standard deviation 21 +/- 11 years) and in 30 healthy control subjects (mean age 24 +/- 7 years). In each subject, 117 chest leads were recorded and maps of the integral values of the QRST interval were calculated. A multipolar distribution of the values, a marker of gross electrical inequalities of repolarization, was found only in 4 patients. To detect minor regional disparities of ventricular recovery, all the ST-T waveforms were analyzed in each subject. The ST-T waves were represented by a discrete series of potential values. The "similarity index" was computed by applying a principal component analysis, which represents (in percent) to what extent 1 fundamental pattern of ST-T reproduces all the recorded waveforms. The mean value of the similarity index was significantly lower in patients with long QT syndrome than in control subjects (49 +/- 10 vs 77 +/- 8%, p less than 0.0001). A value less than 61% (corresponding to 2 standard deviations below the mean value for controls) was found in 35 of 40 patients and in only 1 control subject (sensitivity 87%, specificity 96%). Thus, the similarity index is a more sensitive marker than the multipolar distribution of QRST integral maps in revealing electrical disparities of the ventricular recovery times.(ABSTRACT TRUNCATED AT 250 WORDS)