[Vasovagal syncope and increased baroreceptor activity: evidence for increased sensibility of the baroreflex and its rapid reversal with acute administration of metoprolol]. / Sincope vasovagale e iperfunzione barorecettoriale: evidenza, nelle prime ore dalla sincope, di un incremento della sensibilità baroriflessa e sua rapida regressione mediante somministrazione acuta di metoprololo.

In 17 patients suffering from recurrent episodes of vasovagal syncope as well as in 21 healthy subjects without clinical episodes of presyncope or syncope, we evaluated the reflex decrease in heart rate evoked by the phenilephrine test. In the syncopal patients, the measurements were taken 4-12 hours after the clinical appearance of syncope. We divided the syncopal patients as follows: 9 patients, undergoing pharmacological treatment, and 8 untreated patients (drug free arm). In the pharmacological arm of the study, an alternate, randomized administration of metoprolol (150 mg twice daily for 2 days) and verapamil (80 mg every 6 hours for 2 days) was provided. Therefore, in the pharmacological arm as well as in drug free patients, we tested again the baroreflex sensitivity, by means of iv phenilephrine bolus, 3 and 7 days after the clinical appearance of the syncopal event. The baroreflex sensitivity values were significantly higher in the syncopal group compared to the control group (21 +/- 5 vs 13 +/- 4.5 ms/mm Hg; p < 0.01). Of the two tested drugs, only the metoprolol produced a fast (day 3) decrease in baroreflex sensitivity. On the basis of measurements taken after 7 days, we noted a pattern of widespread reduction in baroreflex sensitivity values, found in both treated and untreated patients. In conclusion, patients with vasovagal syncope exhibited a more pronounced maximal parasympathetic activation compared to the control group. The high baroreflex sensitivity values were soon (day 3) reduced by metoprolol, but not by verapamil therapy; a spontaneous normalization in baroreflex sensitivity values was found 7 days after the clinical episode, regardless of therapy.

[Hypotension during acute myocardial infarct. Different pattern of parameters of renal function in relation to the localization of necrosis]. / Ipotensione durante IMA. Diverso contegno di alcuni parametri di funzione renale in rapporto alla sede di necrosi.

BACKGROUND: The influence on renal function caused by acute myocardial infarction complicated by hypotension has been studied. Particularly, a possible difference in renal functional pattern related to different localization and/or extension of necrotic myocardial area was investigated. METHODS: The study has been performed in 12 cases of acute myocardial infarction, involving anteroseptal (7) or inferodorsal (5) myocardial wall. The score of parietal asynergy resulted 13.28 in anterior vs 7.6 in inferior localization (p < 0.001). RESULTS: The decrease in systolic pressure, conversely, resulted not significantly different in the two groups. The renal function was assessed by measuring the urinary output (V) and creatinine clearance (CrCl). During the first 24 hours, both parameters resulted more preserved in inferior than in anterior AMI (V-552 vs 214 ml; p < 0.005; CrCl 70.6 vs 33.42; p < 0.001). Thus 1) the pressure decrease resulted unrelated to the size of asynergy and 2) the markers of renal function, although the decrease in brachial pressure has been identical in the two groups, have been shown to decrease more profoundly in the anterior infarction. DISCUSSION AND CONCLUSIONS: This may depends upon the reflex interruption of efferent nervous sympathetic drive toward the renal arteriolar bed, occurring in inferior infarction, despite of the systemic hypotension, and able to exercising a beneficial influence on the glomerular filtration rate (GFR). This reflex modulation has been demonstrated as effective in the inferior, but not in the anterior localization of infarction, this different haemodynamic pattern being able to explain the more pronounced decrease in GFR and diuresis in anterior than inferior AMI, as observed in our study.