ATRIAL LATE POTENTIALS - PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA VERSUS PAROXYSMAL ATRIAL-FIBRILLATION

The artial signal averaged electrocardiogram has been used to detect patients at risk for paroxysmal atrial fibrillation but not yet for paroxysmal supraventricular tachycardia. The P-wave-triggered signal-averaged electrocardiogram, during sinus rhythm, was obtained from 97 subjects divided in groups as follows: 30 controls (Group C), 38 patients with documented paroxysmal atrial fibrillation (Group A) and 29 with documented paroxysmal supraventricular tachycardia (Group B). The atrial duration, root mean square of last 20 and 30 ms and the P-QRS segment were measured. Atrial late potentials were considered to exist when: atrial duration was > 120 ms and root mean square of last 20 ms were < 3.5 muV. The atrial duration (ms) was significantly shorter (P < 0.00 1) in Group C (113.4 +/- 8) than in Group A (138.5 +/- 23.8) and Group B (134.3 +/- 14.3). The root mean square (muV) of last 20 ms was significantly higher (P < 0.001) in Group C (5.2 +/- 2.5) than in Group A (2.5 +/- 1.3) and Group B (3.1 +/- 1.8). Atrial late potentials were present in 3/30 controls, 32/38 of Group A cases and 23/29 of Group B. The specificity and sensitivity were, respectively: 0.90, 0.84, for Group A, and 0.90, 0.79 for Group B. The P-QRS segment (ms) was significantly shorter (P < 0.01) in Group B (12.5 +/- 9.4) than in Group C (32.5 +/- 16.9) and Group A (20.5 +/- 13.4). These findings suggest that (a) atrial late potentials could be useful not only for detecting patients at risk for paroxysmal atrial fibrillation but for paroxysmal supraventricular tachycardia as well (b) P-QRS segment might be used for distinguishing paroxysmal atrial fibrillation from paroxysmal supraventricular tachycardia signal averaging

Mechanical ventilation in conjunction with the intra-aortic balloon pump improves the outcome of patients in profound cardiogenic shock

Objective:To examine the effects of mechanical ventilation with positive end-expiratory pressure (PEEP), in conjunction with the intra-aortic balloon pump (IABP), on the outcome of patients in profound cardiogenic shock. Patients: Twenty-eight consecutive patients presenting with myocardial infarction complicated by cardiogenic shock refractory to medical therapy, including dobutamine, dopamine and fluid administration. Eighteen patients were assisted by the IABP alone (IABP group), and ten patients by the IABP plus controlled mechanical ventilation with PEEP set at 10 cmH(2)O (IABP + CMV group). Results: Weaning from mechanical assistance was accomplished in 8 out of 18 patients in the IABP group versus 9 out of 10 patients in the IABP + CMV group (p = 0.04). Ultimately, 5 of 18 patients in the IABP group were discharged from the hospital versus 8 of 10 patients in the IABP + CMV group (p = 0.01). Conclusion: Mechanical ventilation with PEEP at 10 cmH(2)O supplements the IABP and may improve the survival rates of patients suffering from cardiogenic shock

Evolution of late potential parameters in thrombolyzed acute myocardial infarction might predict patency of the infarct-related artery

The objective was to predict the potency grade of an infarct-related artery by identifying the time course of the changes of the late potential parameters before, during, and shortly after thrombolysis. The study population consisted of 51 patients with acute myocardial infarction (AMI) who received thrombolytic therapy within 3.2 +/- 1.3 hours from the onset of symptoms. Multiple signal-averaged electrocardiograms (SAECGs) were recorded before, during, and shortly after thrombolysis. A total of 489 single-averaged electrocardiographic tracings were evaluated. Late potentials were defined as: QRS duration > 114 ms, low amplitude signals (LASs) > 38 ms, and root mean square (RMS) < 20 mu V, Late potentials were found in 37% of patients (21 before and 16 during the first 2 hours of thrombolysis), disappeared in all of patients within 89 +/- 75 minutes (range 25 to 350) but reappeared and persisted in 12% of patients, all with an occluded artery (grade 0). The late potential parameters (QRS, LAS, RMS) showed a gradual improvement which occurred earlier (2 vs 4 hours) and was more marked (0.01 vs 0.05) in cases with a patent artery. This improvement expressed by the late potential parameter index (LnQRS + LnLAS - LnRMS) predicts the patent artery with a sensitivity of 0.94 and specificity of 0.79. The improvement of late potential parameters jointly with close to normal initial values or the late potential parameter index and its changes constituted a satisfactory prediction of the potency grade. Thus, the signal-averaged electrocardiographic technique is capable of predicting the early success or failure of thrombolytic therapy. (C) 1997 by Excerpta Medica, Inc

Spectral analysis of heart rate variability in the sepsis syndrome.

Sympathetic and parasympathetic activity was evaluated on 39 occasions in 17 patients with the sepsis syndrome, by measurement of the variation in resting heart rate using frequency spectrum analysis. Heart rate was recorded by electrocardiography and respiratory rate by impedance plethysmography. The sepsis syndrome was established on the basis of established clinical and physiological criteria. Subjects were studied, whenever possible, during the period of sepsis and during recovery. Spectral density of the beat-to-beat heart rate was measured within the low frequency band 0.04 to 0.10 Hz (low frequency power, LFP) modulated by sympathetic and parasympathetic activity, and within a 0.12 Hz band width at the respiratory frequency mode (respiratory frequency power, RFP) modulated by parasympathetic activity. Results were expressed as the total variability (total area beneath the power spectrum), as the spectral components normalized to the total power (LFPn, RFPn) or as the ratio of LFP/RFP. During the sepsis syndrome, total heart rate variability and the sympathetically mediated component, LFPn were significantly lower than during the following recovery phase (ANOVA, p < 0.0001, p < 0.01 respectively). Both APACHE II (Acute Physiological and Chronic Health Evaluation) and TISS (Therapeutic Intervention Scoring System) scores showed an inverse correlation with total heart rate variability, logLFP, LFPn and the LFP/RFP ratio (p < 0.002 to 0.0001). Sympathetically mediated heart rate variability was significantly lower during the sepsis syndrome and was inversely proportional to disease severity

Autonomic control of the heart and peripheral vessels in human septic shock.

OBJECTIVE: Circulating endotoxin impairs the sympathetic regulation of the cardiovascular system in animals. We studied the changes in the autonomic control of the heart and circulation during septic shock in humans. DESIGN: 12 patients (age 43.0 +/- 6, 17-83 years) were investigated during septic shock (mean duration: 3.5 +/- 0.5 days) and during recovery, fluctuations in R-R interval, invasive arterial pressure (AP) and peripheral arteriolar circulation (PC, photoplethysmography) were evaluated by spectral analysis as a validated noninvasive measure of sympathovagal tone. Apache II score was adopted as the disease severity index. Low frequency components (0.03-0.15 Hz) of the frequency spectra were expressed as relative to the overall variability (LFnu) for each cardiovascular variable. RESULTS: LFnu were low or absent during shock but, in the 10 patients who recovered, increased by the time of discharge (post-shock). R-R LFnu increased from 17 +/- 6 to 47 +/- 9 (p < 0.03), AP LFnu from 6 +/- 3 to 35 +/- 4 (p < 0.02) and PC LFnu from 18 +/- 3 to 66 +/- 4 (p < 0.001). Apache II fell from 23.1 +/- 1, at admission, to 14.8 +/- 1.8 at discharge (p < 0.005). Two patients died showing no LFnu increase. CONCLUSION: Reduced LF components of the variability of cardiovascular signals are characteristic of septic shock, confirming the presence of abnormal autonomic control. Restored sympathetic (LF) modulation seems to be associated with a favourable prognosis

EFFECT OF PROTRACTED DOBUTAMINE INFUSION ON SURVIVAL OF PATIENTS IN CARDIOGENIC-SHOCK TREATED WITH INTRAAORTIC BALLOON PUMPING

The survival of subjects with postmyocardial infarction cardiogenic shock treated with intra-aortic balloon pumping (IABP) differs significantly among various reports. Differences in the criteria for IABP application and in the timing of its initiation have been considered as the main reasons for variations in survival. This study examines whether the way patients in cardiogenic shock are treated prior to IABP may affect their survival. Fifty-five patients in severe postmyocardial infarction cardiogenic shock were classified into three groups according to the rate of dobutamine infusion prior to IABP: the ‘’nondobutamine” (group A, n = 31), the ‘’high-dose dobutamine” (8 to 20 mug-kg-1.min-1, group B, n = 17), and the ‘’low-dose dobutamine” (up to 7 mug-kg-1 -min-1, group C, n = 7). All subjects seen from 1978 to 1983 were recruited for group A, from 1986 to 1990 for group B, and in years 1984, 1985, and 1991 for group C, without using any other classification criteria. It was shown a posteriori that the three groups did not differ in the features of the subjects, in the severity of shock, and in the time length between onset of shock and pumping initiation. None of the 17 subjects of group B could survive under pumping, while 10 of the 31 subjects in group A and 4 of the 7 subjects in group C were weaned off pumping. Conclusions: A protracted, high-dose pre-IABP administration of dobutamine may adversely affect the survival of patients with postmyocardial infarction cardiogenic shock

Macrovascular disease of coronaries and cerebral arteries in streptozotocin-induced diabetic rats. A controlled, comparative study

The aim of this study was to demonstrate the macrovascular disease in streptozotocin-induced diabetic rats and assess any possible differences between the histopatholological changes of the coronaries and cerebral arteries. Hearts and brains were obtained after 4 weeks (short-term experimental diabetes, 10 rats) and 12 weeks long-term experimental diabetes, 10 rats) of streptozotocin injection. Sham injected, control rats were studied in parallel. Muscular-type arteries of 0.10-0.15 mm were examined and semiquantitatively classified either as normal, or slightly, or moderately, or severely thickened by light microscopy: While the arterial wall appeared normal in all sham-injected rats, a varying degree of hyperplasia of the muscular layer and deposition of fibrinoid material resulting in arterial stenosis was prominent in streptozotocin-injected rats. In the group of short-term diabetes there was a slight thickening of the cerebral arteries in the majority of the rats (8/10 rats), while thickening of the coronaries was moderate (9/10 rats). Further progression of arterial wall thickening in both cerebral and coronary arteries was observed in the long-term diabetic group. The mean severity of lesions was significantly higher in the coronaries than in cerebral arteries, both in the short-term (p < 0.0005) and long-term diabetes (p < 0.02). Moreover, by paired statistics within individual animals, we confirmed that wall thickening was significantly more severe in coronaries than cerebral arteries in both groups. These findings suggest an accelerated progress of macrovascular disease in the heart as compared to the brain in the streptozotocin-induced diabetic rat. Although histopathological changes in humans do not always mirror clinical severity, the differences in the macrovascular disease between heart and brain in experimental diabetes may be relevant to the higher relative risk of myocardial infarction compared to stroke for people with diabetes, as compared to people without diabetes