摘要:

We studied the renin and the circulatory responses to unilateral reduction of the renal perfusion pressure (RPP) in seven normotensive subjects and 17 patients with primary hypertension who required diagnostic renal angiography. A balloon-tipped catheter was used for occlusive arteriography; the same catheter was also used to reduce, through appropriate inflation of the balloon, the RPP by 50% of control. In preliminary observations, this stimulus was shown to be safe and strong enough to activate renin release maximally. The reduction in RPP (either right or left) was maintained for 60 minutes. Plasma renin activity was determined after 1 hour of recumbency (baseline), at various periods during occlusion of the vessel, and after release. Cardiac output was measured at the same periods, and systemic arterial pressure and heart rate were monitored continuously.As regards the renin response, we observed that (1) systemic (arterial) renin was already significantly augmented at 5 minutes, reached a peak at 15 minutes and then tended to decrease, although the mean values continued to be markedly higher than the baseline values; (2) soon after the stimulus, venous renin and venous arterial difference of the occluded kidney became definitely elevated and remained elevated for the duration of the occlusion; (3) on the contralateral side, the venous arterial difference decreased progressively until 30 minutes after occlusion, when it was almost abolished, indicating that renin release from the nonoccluded kidney was suppressed; and (4) the response was quantitatively and qualitatively similar in normotensive and hypertensive subjects. Despite this humoral reaction, in no case did systemic arterial pressure, heart rate and cardiac output change throughout the studies.We conclude that in man, either normotensive or hypertensive, unilateral RPP reduction duplicates the renin pattern of the Goldblatt kidney, but does not duplicate the circulatory response. This evidence applies to 1-hour renal artery occlusion and does not exclude the possibility that renin may have a role in the blood pressure elevation after long-standing renal arterial stenosis.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARYSwimming is frequently recommended for cardiac rehabilitation, but little is known of its physiologic consequences in ischemic heart disease. Eight males who had had a myocardial infarction 8–17 months before the study were exercised to exhaustion or angina with 10 W/min−1ramp on a cycle ergometer in sitting and supine positions. Oxygen uptake (V02) was continuously measured to monitor the physiologic power requirement. All eight patients were taking β blockers and four were taking digoxin. During sitting cycling, angina occurred in four and ST depression in five; during supine cycling, angina occurred in five and ST depression in six. VO2 was then measured while they swam at their own comfortable speed (mean 0.43 m/sec−1) in a swimming flume at water temperatures of 25.5°C and 18°C. In six, the water speed was gradually increased until they were limited by symptoms. Comfortable swimming at 25.5°C was 87% (1.28 1/min−1) and at 18°C 89% (1.30 1/min−1) of sitting peak V02, while heart rates were 92% and 91% respectively. The mean peak VO2 and heart rate did not differ significantly between bicycle and swim tests (peak VO2 sitting 1.49 ± 0.23, supine 1.42 ± 0.24, 25.5°C 1.60 ± 0.17, 18°C 1.52 ± 0.19 1/min−1). Only two patients reported angina while swimming in warm water and one in cold water, although ST depression occurred in six in both swims. The subjective comfort and large muscle groups involved make swimming a good exercise, but the high relative energy cost and failure to identify ischemic symptoms indicate caution in cardiac patients, especially if their swimming skills are poor.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Multivariate linear discriminant function analysis on maximal exercise treadmill and angiographic data from 500 men with definite angina, 584 men with probable angina and 267 men with nonspecific chest pain identified independent predictors of presence and extent of coronary disease. We used the discriminant function to develop a clinical risk index and a clinical and exercise risk index for each patient subset. Probability curves were generated to predict the presence and extent of coronary disease. In definite angina cases, exercise testing provided more diagnostic information than clinical data alone. However, in the 10% of cases with the smallest risk indexes, half of the patients had coronary disease and one-quarter had multivessel disease. In men with probable angina, exercise testing added substantially more diagnostic information than clinical data. The probability of multivessel disease was reduced to less than 10% for 30% of patients with probable angina, an important diagnostic contribution. Exercise testing in men with nonspecific chest pain was of limited value because disease prevalence was already low.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Forty-nine patients in whom percutaneous transluminal coronary angioplasty (PTCA) was attempted were evaluated by thallium-201 myocardial scintigraphy after exercise and at rest before the intervention. After successful PTCA of a single stenosis in a native vessel (30 of 44 patients) and of a stenosis in an aortocoronary bypass graft (three of five patients), scintigraphy was repeated within 3 weeks in 30 patients. Long-term follow-up studies by scintigraphy at 5–6-month intervals up to more than 2 years (mean follow-up 18 months) were performed in 16 patients.Before PTCA, clear-cut regions of decreased thallium-201 activity were observed in 43 of 49 patients. Thallium-201 activity within this zone was reduced to 74 ± 1% (SEM) of maximal myocardial thallium-201 activity after exercise, but returned to normal (> 80%) at rest (88 ± 1%,p< 0.001). After PTCA, no distinct defects were recognizable in the region of previously decreased thallium-201 activity, and the respective values were 89 ± 1% after exercise at identical work loads (p< 0.001 compared with the corresponding values before PTCA) and 94 ± 1% (p< 0.01) at rest. These results paralleled the angiographic findings, which showed an increase in luminal diameter in the stenotic segment of the treated vessel from an average of 15 ± 2% of the pre- and poststenotic vessel diameter before PTCA to 67 ± 3% (p< 0.001) after PTCA. During long-term follow-up, thallium-201 activity remained normal after exercise in the entire heart in 13 of 16 patients. In three patients, a new defect in the same location as before treatment reappeared 4–12, 6 and 29–12 months after PTCA because the stenosis recurred, as documented by angiography.We conclude that thallium-201 exercise scintigraphy permits the best documentation of the ongoing changes in myocardial perfusion after PTCA.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Thirty-three patients with coronary artery disease (CAD) and 13 subjects without demonstrable cardiac disease were studied with multigated equilibrium blood pool imaging to assess the diagnostic value of exercise-induced alterations in left ventricular (LV) volumes, segmental wall motion, ejection fraction (LVEF), and the end-systolic pressure-volume relationship. In subjects without cardiac disease, left ventricular end-diastolic volume (LVEDV) was 102 ± 7.2 ml (SEM) at rest and 125 ± 9.7 ml at peak exercise (PEx) (p< 0.001). Left ventricular end-systolic volume (LVESV) was 35 ± 3.0 ml at rest and 29 ± 3.4 ml at PEx (p< 0.01). LVEF increased from 0.72 ± 0.02 at rest to 0.82 0.02 at PEx (p< 0.001). The nine patients with one-vessel CAD also had an increase in LVEDV (p< 0.001) and LVEF (p< 0.02) at PEx, but no significant change in LVESV. The 24 patients with significant two- or three-vessel CAD had increases in both LVEDV (169 ± 13.2 ml to 195 ± 13.7 ml,p< 0.001) and LVESV (86 ± 12.0 ml to 102 ± 12.0 ml,p< 0.01) at PEx and a decrease in LVEF (0.56 ± 0.03 to 0.52 ± 0.03,p< 0.05). The relationship between cuff-determined peak systolic blood pressure and LVESV index (P/V index) was used to further characterize alterations in LV function at rest and during PEx. In subjects without cardiac disease, this index rose substantially during PEx (7.6 ± 0.73 at rest vs 14.9 ± 1.78 with PEx,p< 0.001). This change was less dramatic in those with one-vessel disease and absent in patients with two- or three-vessel disease (4.2 ± 0.60 at rest vs 3.9 ± 0.50 at PEx, NS). The change in LVESV alone was different in each group. We conclude that the assessment of exercise-induced alterations in LVESV and the P/V index is useful for evaluating LV dysfunction associated with angiographically important coronary artery disease.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The clinical value of combining exertional ECG and postexertional thallium (201T1) scintigraphy was assessed in 160 patients (130 men and 30 women) suspected of having coronary artery disease (CAD) who underwent a coronary arteriography. Based on sex and history, the patients were subdivided in two groups with different prevalences of CAD: Group 1 (high prevalence of CAD = 90%) included 98 men with typical angina pectoris (AP) and group 2 (low prevalence of CAD = 18%) included 32 men and 30 women with atypical AP.Compared with the exertional ECG, myocardial scintigraphy was more sensitive (87% vs 74%) and more specific (89% vs 70%) for the diagnosis of CAD. The combination of the ECG and scintigraphic data was useful if both tests gave concordant results: 100% of true positives (n = 67) and 84% of true negatives (n = 43). In case of discordant results (n = 50), no firm diagnostic conclusion could be made due to the many false-positive (27%) and false-negative (25%) scintigrams.These results are easier to interpret when the prevalence of CAD is taken into account. According to Bayes' theorem, abnormal exercise results confirm CAD when the prevalence is high and normal results rule out CAD when the prevalence is low; also, a normal response to exercise has no predictive value when the prevalence is high. When the prevalence is low, an abnormal ECG or thallium has low predictive value but concordant abnormal responses are highly predictive for CAD (100% of true positives).

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Numerous criteria for the diagnosis of inferior wall myocardial infarction by electrocardiogram (ECG) and vectorcardiogram (VCG) have been published, but they have not been subjected to a systematic, independent evaluation. Accordingly, we studied 146 patients undergoing cardiac catheterization; 63 were normal and 83 had a history of infarction, a significant right coronary lesion and an inferior wall motion abnormality (inferior infarction group). No ECG or VCG criteria were considered in the designation of the two groups; rather, three sets of ECG and VCG criteria were evaluated for this purpose. Specificity was excellent (98–100%) and sensitivity was poor (4–34%) by all three sets of ECG criteria, but the 1949 ECG criteria of Meyers et al. are the least sensitive (4%,p< 0.001). Specificity (90–100%) and sensitivity (82–84%) were very good by all three VCG criteria. The VCG criteria of Starr et al. gave no false-positive results in our normal group. Because of enhanced sensitivity, the overall accuracy of the VCG was higher than that of the ECG for the diagnosis of inferior infarction (90% vs 62%,p< 0.001). We conclude that more recent ECG criteria for the diagnosis of inferior wall myocardial infarction are highly specific, but insensitive compared with VCG criteria.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Exercise or isoproterenol infusion may evoke ventricular arrhythmias in patients with the long QT syndrome. We examined the electrocardiographic effects of the Valsalva maneuver in eight patients with the long QT syndrome and nine healthy subjects. The Valsalva maneuver lengthened the QTc interval in both groups, but the lengthening was greater in the patients. In the patients who were having frequent attacks of ventricular tachycardia, the Valsalva-induced prolongation of the QTc interval was particularly remarkable and was associated with the development of T-wave alternans and short runs of ventricular tachycardia. Propranolol effectively suppressed the lengthening of the QTc interval during Valsalva strain and prevented Valsalva-induced ventricular arrhythmia. These results suggest that the Valsalva maneuver may be useful in evaluating the risk of ventricular tachyarrhythmias and the efficacy of drug treatment in patients with the long QT syndrome.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Diltiazem, verapamil and nifedipine suppress sinoatrial (SA) nodal function in the excised rabbit heart. Clinically, however, their suppressive effect on the SA node is modified considerably by the reflex increase in sympathetic tone as a result of the fall in blood pressure caused by the vasodilating action of the calcium antagonists.Diltiazem, verapamil and nifedipine suppress atrioventricular (AV) nodal conduction and prolong refractory periods in the excised rabbit AV node. Clinically, diltiazem and verapamil exert a similar suppressive effect on the AV node and are useful for treating and preventing AV nodal reentrant tachycardia. Nifedipine, in clinically practical doses, has no antiarrhythmic properties, probably because of reflex activation of the sympathetic system secondary to its hypotensive effect, which is greater than that of the other two calcium antagonists.Diltiazem and verapamil may sometimes worsen AV conduction, especially in patients with conduction disturbances. Nifedipine, on the other hand, can be used as a coronary vasodilator with the least untoward effect on AV conduction.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

This report details our experience with documented chronic second-degree atrioventricular (AV) nodal block (proximal to His [H]) in 56 patients. Forty-six men (82%) and 10 women (18%), ages 18–87 years, were studied. Nineteen of the patients (34%) had no organic heart disease (including seven trained athletes) and 37 (66%) had organic heart disease. ECGs in all patients demonstrated episodes of type I seconddegree block; five patients also had periods of 2:1 block. Prospective follow-up of patients with no organic heart disease (157–2280 days, mean 1395 636 days) revealed one patient with clear indication for permanent pacing because of bradyarrhythmic symptoms (permanently placed on day 220 of follow-up). Two patients died nonsuddenly.In patients with organic heart disease (prospective follow-up of 60–2950 days, mean 1347 ± 825 days), pacemakers were implanted in 10 patients, primarily for treatment of congestive heart failure in eight and syncope in two. Sixteen patients died three suddenly, seven with congestive heart failure, two of an acute myocardial infarction and four of causes unrelated to cardiac disease.In summary, chronic second-degree AV nodal block has a relatively benign course in patients without organic heart disease. In patients with organic heart disease, prognosis is poor and related to the severity of underlying heart disease.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID