摘要:

The inhibition of slow-channel activity in vascular smooth muscle and myocardium produces a wide range of beneficial effects in various cardiocirculatory disorders, such as arrhythmias, myocardial ischemic syndromes and hypertension. As in the case of β, B antagonists, slow-channel inhibitors constitute a heterogeneous group with a variable degree of selectivity for heart muscle, atrioventricular conduction, peripheral vessels and the coronary circulation. Their hemodynamic effect is the net result of a complex interplay of simultaneous changes in heart rate, preload, afterload, contractility and coronary blood flow. In animals, these agents reduce myocardial ischemic injury and may enhance collateral perfusion; in man, they have salutary effects in exertional angina in which they probably act by reducing cardiac work, an effect quantitatively not dissimilar to that produced by β antagonists. This approach thus provides an alternative mode of medical therapy for patients with exertional angina who do not tolerate d β blockers or in whom β blockers are contraindicated by the presence of bronchospasm or peripheral vascular disease. However, the major additional advantage that slow-channel antagonists unquestionably have over β blockers is the fact that they all are potent coronary vasodilators. In contrast,β antagonists constrict coronary vessels. For this reason, the advent of slow-channel inhibitors such as verapamil, nifedipine and diltiazem is a very timely landmark in relation to the wealth of data that have confirmed the belief that coronary vasospasm plays an important role not only in the pathogenesis of classic variant angina, but also in many patients with unprovoked angina, myocardial infarction or sudden death in the setting of diseased as well as normal coronary arteries. For a patient who has normal or relatively normal coronary vessels but who develops vasospastic angina, slow-channel inhibitors are likely to become the agents of choice and preliminary clinical experience is in line with these considerations. Similarly, patients who have exertional and vasospastic angina are more likely to derive greater behefits from slow-channel inhibitors than from β blockade, which may aggravate coronary spasm. Evidence also indicates that certain slow-channel antagonists may be useful in other cardiocirculatory disorders, such as acute pulmonary edema, acute hypertensive emergencies and obstructive cardiomyopathies. Such indications, if confirmed, will broaden the clinical usefulness of this class of compounds, whose introduction is likely to be a significant advance in cardiovascular therapeutics.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We analyzed the ordering and impact of the first 171 fee-for-service cardiovascular nuclear medicine procedures at one hospital. The ordering physicians said 72% of the study results were useful and 28% contributed to changes in patient management. Experienced cardiology reviewers, however, felt that only 65% of studies were appropriately ordered, that 97% of appropriately ordered studies provided potentially useful information, and that 12% of all studies made important contributions to appropriate changes in patient management. The reviewers were most likely to rate exercise thallium procedures and procedures ordered by physicians from distant hospitals as being appropriately ordered and having important clinical impact. We conclude that (1) ordering physicians and reviewers may disagree substantially in their estimates of the impact of a diagnostic test; and (2) although a test may yield important information in appropriate patients, its total clinical impact will depend on how often it is suitably ordered and used.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

To assess the influence of the autonomic nervous system upon the recovery of the normal human sinus node, the responses to overdrive pacing at multiple cycle lengths of the denervated donor heart sinus nodes of 18 human cardiac transplant recipients were compared to the responses of those 18 patients' innervated, remnant atria and of 20 control subjects with normal sinus node function. The mean average spontaneous sinus cycle length of the donor atria (643 ± 78 msec [SD]) was significantly shorter than that for either the innervated recipient (822 ± 171 msec) or the control atria (840 ± 204 msec). The longest sinus node recovery time occurred after overdrive pacing at cycle lengths of 400 msec or less in 94% of the donor atria, but in only 28% of the recipient atria (p < 0.01) and 10% of the control atria (p < 0.0001). Secondary postpacing cycles were longer than the initial postpacing pause after at least one pacing intervention in only 6% of the donor, but in 78% of the recipient (p < 0.01) and 45% of the control atria (p < 0.01). Curves describing the relationship between the corrected sinus node recovery time and the cycle length of overdrive pacing were smooth and predictable in 72% of the donor atria, but in only 17% of the recipient (p < 0.01) and 20% of the control atria (p < 0.01). In transplant patients pacing was performed for both 60- and 15-second overdrive periods; recovery phenomena were qualitatively and quantitatively the same for the two durations of pacing. We conclude that the cardiac autonomic nervous system has considerable influence on the postpacing recovery phenomenon of the normal human sinus node. This may account, in part, for the insensitivity of the sinus node recovery time in detecting sinus node dysfunction.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Heart rate and blood pressure responses during and after carotid sinus massage were examined in 66 patients just before coronary angiography. A significant relationship was found between heart rate and blood pressure responses and (1) angina pectoris class, (2) total coronary artery disease score and (3) presence of high-grade (> 90%) stenosis of any of the three major coronary arteries. Only patients with contraction abnormalities of the anterolateral left ventricular region had greater cardioinhibitory responses than patients with normal left ventricular angiograms. Among patients with normal left ventricular angiograms, those with more than 50% stenosis of one or more vessels had significantly (p < 0.01) greater responses than those with no or minimal coronary artery disease. All 21 hypersensitive (asystole longer than 3 seconds) patients had significant multivessel coronary artery stenoses or single-vessel high-grade stenosis (> 90%) proximal to the atrioventricular nodal artery. None of the 11 patients with normal coronary arteries had an exaggerated response to carotid sinus massage. These data support the association of an exaggerated response to carotid sinus massage in the presence of symptomatic coronary artery disease and suggest that the magnitude of response is influenced by the severity of the disease.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Adrenergic responsiveness after abrupt propranolol withdrawal during exogenous and endogenous catecholamine stimulation was assessed in 10 normal subjects and 10 patients with angina pectoris. Propranolol, 160 mg/day, was administered for 2 weeks and then stopped. During an epinephrine infusion, heart rate and systolic pressure-heart rate product were significantly reduced from control in the propranolol period (p < 0.005). There were no differences from control 96 hours after the drug had been stopped in both groups or at 144 hours in the angina patients who were studied for a longer time. At 48 hours of withdrawal, heart rate and the pressure-rate product were significantly less than control level in the angina patients, but not in the normal subjects. Similar results were observed during exercise in both groups. The epinephrine-induced increase in free fatty acids was blocked by propranolol (p < 0.005), was still attenuated at 48 hours of withdrawal (p < 0.05), but returned to control levels thereafter in both groups. Resting serum triiodothyronine levels decreased with propranolol (p < 0.005) and remained low throughout the withdrawal period. Measurements of dopamine β, B-hydroxylase, plasma platelet factor 4, and platelet aggregation at rest and after exercise did not change significantly during or after propranolol administration. Plasma norepinephrine and epinephrine values were not changed from control during the withdrawal period at rest or after exercise. We conclude that there is no evidence of hypersensitivity to β-adrenergically mediated responses after abrupt propranolol withdrawal.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The clinical course was followed for 10 years in 521 patients whose coronary arteriograms did not show any severe obstruction. Coronary disease had been suspected in all patients before arteriography. Two of 357 patients thought to have normal arteriograms died from coronary disease and two of 101 patients died who had less than 30% estimated narrowing of at least one coronary artery. Ten deaths ascribed to coronary disease occurred in 63 patients who had 30-50% narrowing of at least one major coronary artery. The difference in death rates between the normal or mildly diseased groups and the group that had moderate narrowing was significant (p < 0.01). Coronary events (death from coronary disease, subsequent myocardial infarction, or arteriographic evidence of progression of coronary obstruction) occurred in 2.1% of those who had normal arteriograms, 13.8% of the group with mild lesions, and 33% of those with moderate degree of coronary arterial narrowing.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

In this study we extended the characterization of outcome in 1214 medically treated patients with coronary disease by considering nonfatal infarction and death together as ischemic events. At 7 years, the cumulative event rate was 47% (18% for nonfatal infarction as the initial event and 29% for death as the initial event). In multivariable analysis of 81 baseline descriptors, 11 (six clinical and five catheterization) were independent predictors of events. Progressive chest pain, number of diseased vessels, left main stenosis and left ventricular (LV) function were the most important predictors. Progressive pain was a more important predictor of total events than of survival alone. In patients with one-, two- or three-vessel disease and normal LV function, nonfatal infarction accounted for at least 50% of initial events. In patients with left main disease or severe LV dysfunction, death was the predominant event. These results have important implications for interpreting the natural history of coronary artery disease.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

In 65 patients with a previous transmural myocardial infarction (anterior in 33, inferior in 32), exercise thallium scanning was compared with 12-lead exercise electrocardiography to see if multivessel disease could be detected. At coronary arteriography 40 patients were shown to have multivessel disease (⩾70% diameter stenosis in two or three vessels) and 25 patients had one-vessel disease. On the exercise scan thallium defects corresponding to the electrocardiographic site of infarction were present in all patients. Patients with one-vessel and multivessel disease were separated by exercise-induced angina, perfusion defects on the exercise thallium scan in more than one specific vascular area, and a positive exercise ECG associated with angina, but not by a positive exercise ECG alone. Of the 40 patients with multivessel disease, 85% had defects in more than one vascular area on the thallium scan and 70% had a positive exercise ECG (p = NS). Of the 37 patients with thallium defects in more than one specific vascular area, 92% had multivessel disease, compared with 72% of the 39 patients who had a positive exercise ECG (p < 0.05). Periinfarctional ischemia was present in 38 of the 65 patients (58%) (14 of 25 with one-vessel disease and 24 of 40 with multivessel disease), and did not correlate with the severity of the corresponding coronary artery disease. When thallium defects that resolved were noted in a second vascular area, they were associated with a resolving rather than a constant defect in the vascular area where the infarction had occurred (p < 0.005). In patients after a transmural myocardial infarction, multivessel disease can be better differentiated from one-vessel disease by thallium scanning than by exercise electrocardiography.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The relations between regional ventricular function and regional and surface ECGs were studied in eight conscious dogs during complete and partial coronary obstructions. Wall thickness and local ECGs were measured using an implanted sonomicrometer, and 11 subcutaneous electrodes were implanted in a modified McFee vectorcardiographic array. Complete obstruction of the circumflex coronary artery (using a hydraulic occluder) produced regional hypokinesia after 15 seconds and regional dyskinesia at 1 minute. Significant ECG changes occurred first in the surface vectorcardiogram, ST segments changed at 30 seconds and mean epicardial and endocardial ECG ST segments increased after 1 minute. During mild partial coronary stenosis that produced stable reductions of systolic wall thickening (%δWT) of less than 25% of control, no ST-segment changes occurred in the surface vectorcardiogram during the 10-minute study period, although ST segments increased significantly in the endocardial and epicardial ECG. With moderate coronary stenoses that produced immediate 25-48% reductions of %δWT (average reduction 36 ± 4%), significant mean ST displacements occurred after 2 minutes in the endocardial ECG, after 3 minutes in the epicardial ECG and after 4 minutes in the surface vectorcardiogram. With coronary stenoses that produced more than 50% reduction of %A. WT (average reduction 69 ± 2%), mean endocardial ST-segment changes were noted after 2 minutes, and changes in both the mean epicardial ECG and the surface vectorcardiogram occurred after 3 minutes. Thus, during mild coronary stenosis, regional myocardial dysfunction can occur without surface ECG changes, while during moderate coronary stenosis, it occurs before endocardial ST-segment changes and precedes surface ECG alterations by several minutes. The surface ECG was slightly more sensitive than the local ECG during complete coronary occlusion and less sensitive during partial coronary obstruction. We conclude that regional contractile abnormalities provide a more sensitive indicator of ischemia than electrocardiographic ST-segment changes.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We quantitatively analyzed the effect of graded left anterior descending and septal coronary flow (LAD + septal flow) reduction on left ventricular function with a left ventricular end-diastolic pressure (LVEDP) of 6 mm Hg and 12 mm Hg. We used an isolated, ejecting, canine heart preparation (n = 8), the coronary flow of which could be controlled independently of the aortic pressure. We kept the other hemodynamic variables — heart rate, left circumflex coronary flow, right coronary flow and aortic input impedance — constant within their normal physiologic range. We considered this reduction in LAD + septal flow to be analogous to that of the most frequent lesion in ischemic heart disease. There was no plateau in the left ventricular work caused by this reduction of the regional coronary flow. Therefore, the plateau commonly reported in previous studies may be partially a result of the compensatory elevation of LVEDP, which is necessary to maintain the left ventricular work.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID