SUMMARY To describe the epicardial ventricular activation sequence in the intact human heart, we obtained epicardial maps from 11 patients with normal QRS undergoing open heart surgery. Epicardial breakthrough (EBT), defined as the emergence of a radially propagating epicardial wavefront, occurred in three to five sites in each patient, and was earliest in the anterior right ventricle, 7-25 msec (mean 17 msec) after the onset of the QRS in all patients. Subsequent EBT occurred in the inferior right ventricle (10 sites in 10 patients), in the anterolateral left ventricle (13 sites in 10 patients), and the inferior left ventricle (eight sites in seven patients). Latest epicardial activation (LEA), defined as the latest site of recordable epicardial activity, occurred in the basal segments in all patients, anteriorly in the right ventricle in five patients, and inferiorly in six patients, four on the right and two on the left. LEA occurred 63-96 msec (mean 77 msec) after the onset of the QRS, and was recorded within 20 msec of the end of the QRS in all patients. Sequence of epicardial activation reflected a fusion process among the wavefronts. This descriptive and quantitative data should provide a suitable basis for comparison of abnormal ventricular activation sequences in patients undergoing surgery for preexcitation or ventricular tachycardia.MOST DESCRIPTIONS of ventricular activation in the mammalian heart are derived from canine experimentation using epicardial and multiple intramyocardial electrodes.'" Sporadic observations have been made in the human heart under a variety of surgical conditions in the last 50 years, relating mostly to unipolar QRS morphology.8-13 In 1970, Durrer et al. described the epicardial and intramural activation sequence in seven extirpated, reperfused human hearts.'4 The activation of the human heart was found to be different in several ways from the dog heart.Extensive epicardial mapping of the intact human heart has become feasible, as a result of the experience gained with mapping of patients with cardiac arrhythmias. In this study, we systematically report observations of epicardial activation in the intact human heart, describing and quantitating the range of normality in epicardial activation sequence in 11 patients undergoing open heart surgery. Material and Methods Patient SelectionWe reviewed ECGs of patients scheduled for open heart surgery at

SUMMARY During periods of tachycardia induced by atrial pacing in eight patients, moderate increments in dP/dt(max) and (dP/dt)/CPIP (common produced intraventriciilar pressure) and moderate reductions in left ventricular ejection time (LVET) and Q-S2 were demonstrated. These changes varied between individuals, but reduction in systolic intervals was consistently less than that reported from populations showing a range of resting heart rates. Individual regression formulae relating each variable to paced heart rate were used to calculate rate-dependent and rate-independent changes induced by isoprenaline and ouabain. Despite technical difficulty in precise measurement of systolic intervals, there was an excellent inverse correlation between rate-independent changes in Q-S2 and in both dP/dt(max) and (dP/dt)/CPIP. Rate-independent change in Q-S2 appears to be a practical, moderately sensitive, and reasonably precise measure of the inotropic effect of a drug which does not radically alter left ventricular end-diastolic pressure or blood pressure; Day-to-day variation in systolic intervals may limit the use of the technique to studies of short duration.Determination of the inotropic activity of a drug essentially belongs to the animal laboratory, but confirmation of this activity, and particularly characterisation of its dose-response effects in man, is a necessary prelude to its rational clinical employment. Direct measurement of changes in contractile activity and pumping function of the left ventricle presently furnish the most accurate indication of alterations in inotropic activity.1-3 Cardiac catheterisation, however, is cumbersome, limited by ethical considerations, and often of such brevity as to preclude the measurement of duration of activity of a drug or its dose-response effects. Non-invasive methods have therefore been sought as a means of making repeated measurements of left ventricular activity; among such methods measurement of the duration of the various components of systole has been the most widely acclaimed.46 The utility of these methods, however, in evaluating changes in left ventricular activity induced by drugs has yet to be fully tested. It was the purpose of this study, therefore, to evaluate the precision by which measurements of non-invasive systolic time intervals reflect changes in intraventricular pressure before and after the administration of drugs known to increase motropic activity. Subjects and methodsFour normal subjects (aged 20 to 35 years), and six male and two female patients (aged 23 to 45 years) admitted for the investigation of chest pain were studied. All were in sinus rhythm. In the patients, radiographic cardiac silhouette was normal. Electrocardiograms at rest and during treadmill exercise up to heart rates of 160 beats per minute were normal in all. Left ventricular end-diastolic pressure during supine leg exercise did not exceed 25 mmHg. None was receiving drugs at the time of the study. Informed consent was obtained from all patients. DESIGN OF INVESTIGATIONThe fou...

No abstract

The effects of single and combined selective blockade of the sympathetic alpha-and beta-receptors were examined in patients with severe hypertension (diastolic pressure > I20 mmHg) uncomplicated by cardiac or renal failure. Given In uncomplicated essential hypertension the raised blood pressure is accompanied by a normal cardiac output (Taylor, Donald, and Bishop, I957). The increased peripheral resistance is uniformly distributed throughout all the regional circulations and resides predominantly in the peripheral arterioles (Freis, I960). These vessels regulate the resistance in many of the regional vascular beds, and particularly in the kidney, through sympathetic alphaadrenergic receptors (Moran, I966).Thus it is reasonable to expect that drugs which possess both vasodilator properties and also the ability to inhibit stimulation of the adrenergic alpha-receptors may offer substantial advantages over other less specific agents in the treatment of hypertensive vascular disease. Phentolanine, an alpha-receptor antagonist with conspicuous vasodilator properties (Taylor et al., i965a, b; Majid, Sharma, and Taylor, 197i), has been shown to be effective in acutely lowering the blood pressure of hypertensive patients (Taylor et al., i965a I965a; Majid et al., 197I). For this reason it is logical to combine drugs that block both the alphaand beta-adrenoreceptors so that the reflex increase in sympathetic stimulation of the heart that occurs in response to the fall in blood pressure induced by alpha-receptor blockade is prevented by inhibition of the cardiac beta-receptors.The following investigation was, therefore, undertaken to test this thesis by acute haemodynamic studies in patients with severe hypertensive disease and to determine the clinical effectiveness of the combination of oral alpha-and beta-receptor antagonists in the longer term treatment of these patients.Patients and methodsTwelve patients with severe uncomplicated essential hypertension were studied. Five were men, average age 47 years (range 44 to 50 years) and average weight 89 kg (range 84 to 98 kg); 7 were women average age 41 years (range 34 tO 49 years) and average weight 60 kg (range 49 to 83 kg). Seven patients presented with severe headaches which had proved intractable to other antihypertensive drugs, singly or in combination. In the remainder a high blood pressure was discovered during routine medical examination for minor illnesses. The lowest diastolic pressure measured in the supine position by doctors in the ward persistently exceeded I20 mmHg (range I20 to I50) in all patients during their hospital on 12 May 2018 by guest. Protected by copyright.

No abstract