ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Cross-sectional echocardiographic measurements of normalized septal curvature (NSC), systolic anterior motion of the center of the left ventricular cavity (CAM), and the M mode ratio of left ventricular posterior wall epicardial motion (PEM) to posterior wall thickening (PWT) were made in eight normal subjects, 16 patients with right ventricular volume overload (RVVO) and five with pressure overload (RVPO). Paradoxical M mode septal motion was confined to early systole in six patients with RVVO (group I) and was sustained in 10 (group II). Similar end-diastolic septal flattening was observed in RVVO group I (NSC 0.50 + 0.16 [SDI) and group 11 (0.49 + 0.23) when compared with the normal group (0. 83 + 0.07, both p < .005). NSC increased in both RVVO groups during the first one-third of systole (p < .002) to values not significantly different from normal, but did not change significantly thereafter. CAM in RVVO group 11 (5.4 ± 2.2 mm) exceeded CAM in both the normal group (1.8 + 1.9 mm, p < .001) and group 1 (2.1 ± 1.4 mm, p < .005). Similarly, the PEM/PWT ratios in group LI (mean 2.94; range 2.13 to 8.0) exceeded those in both the normal group (mean 1.59; range 1.11 to 2.13, p < .01) and group I (mean 1.32; range 1.10 to 1.67, p < .01). In the RVPO group, CAM was insignificant, the PEM/PWT ratios were lower than normal (p < .01), and marked enddiastolic septal flattening was incompletely corrected during early systole, after which the septum was flattened further until end-systole (p < .005). Midsystolic septal flattening was also observed in those with RVVO in whom the right ventricular/left ventricular peak systolic pressure ratio exceeded 0.4. Thus, true septal paradox in patients with RVVO is an early systolic event. The apparent persistence of septal paradox beyond early systole is an artifact due to anterior left ventricular translation. These findings help explain the preservation of left ventricular systolic function in RVVO despite apparently sustained septal paradox, support the role of the transseptal pressure gradient in determining septal curvature, and indicate that regional wall motion analysis from a fixed reference point in patients with RVVO is inappropriate.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

A family history of heart attack is reported to be an independent predictor of cardiovascular death in men. In a 9 year follow-up of 4014 adults from 40 to 79 years old in the Rancho Bemardo Study, men under 60 years of age with a family history of heart attack were at fivefold increased risk. In this study, we sought to determine whether modifiable risk factors, i.e., blood pressure, plasma cholesterol, obesity, and cigarette smoking, have a differential effect on cardiovascular risk in those with and without a family history of heart attack. For both sexes, cigarette smoking was a stronger predictor of cardiovascular disease in those with a family history of heart attack (relative risk of smokers vs nonsmokers was 2.5 for men and 4.0 for women) than in those with no such family history (relative risk of smokers vs nonsmokers was 1.1 for men and 1.7 for women). Conversely, an increased risk of cardiovascular mortality in men with a family history of heart attack was present predominantly in smokers (relative risk related to positive family history was 1.2 in nonsmokers, and 3.3 in smokers). An estimated 68% of the excess deaths in men with a family history of heart attack were attributable solely to the interaction of family history with smoking habit and were therefore potentially avoidable. The risk of cardiovascular disease associated with an apparently inherited predisposition appears to be profoundly affected by modifiable behavior.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Lower limb blood flow, oxygen uptake, and femoral vein 02 content were measured at rest and during maximal bicycle exercise, performed with two legs and one leg, in four normal subjects and in five patients with severe congestive heart failure. While in normal subjects femoral vein blood flow and lower limb vascular conductance were significantly greater during one-leg exercise than during two-leg exercise (6084 + 745 vs 5370 + 803 ml/min, p < .05, and 52.3 8.0 vs 45.1 + 8.2 U x 1o3, p < .05, respectively), in patients with severe congestive heart failure these values were similar during the two forms of exercise (1082 ± 459 vs 1053 ± 479 m/min and 9.6 ± 3.7 vs 9.4 + 3.5 U x 103, respectively). In five additional patients, one-leg maximal bicycle exercise was performed before and after administration of phentolamine into the femoral artery of the active leg. Regional a-adrenergic blockade with phentolamine did not alter maximal oxygen uptake attained during one-leg bicycle exercise (9.8 ± 1.5 vs 10.3 ± 1.9 ml/kg). Lower limb blood flow and femoral vein 02 content attained during maximal one-leg exercise were also similar before and after phentolamine. Thus, in contrast with normal subjects, patients with severe congestive heart failure were unable to further increase limb blood flow during one-leg bicycle exercise. Moreover, local a-adrenergic blockade does not augment blood flow to the active limb during maximal one-leg bicycle exercise. This suggests that the ability of the muscular vasculature to vasodilate during exercise is impaired and may be a limiting factor to maximal exercise capacity in such patients.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

More than 3600 white men, from 30 to 79 years old and without a history of myocardial infarction, underwent submaximal treadmill exercise tolerance tests as part of their baseline evaluation for the Lipid Research Clinics Mortality Follow-Up Study. The exercise test was conducted according to a common protocol and coded centrally; depression of the ST segment by at least 1 mm (visual coding) and/or 10, V-sec (ST integral, computer coding) signified a positive test. Concurrent measurements of age, blood pressure, history of cigarette smoking, and plasma levels of lipids, lipoproteins, and glucose, as well as other coronary risk factors, were obtained. Cumulative mortality from cardiovascular disease was 11.9% (22/185) over 8.1 years mean follow-up among men with a positive exercise test vs 1.2% (36/2993) over 8.6 years mean follow-up among men with a negative test. Threequarters (43) of these deaths were due to coronary heart disease. The relative risk for cardiovascular mortality associated with a positive exercise test was 9.3 before and 4.6 after age adjustment. Cardiovascular mortality rates were especially elevated (relative risk 15.6 before and 5.1 after age adjustment) among the 82 men whose exercise tests were adjudged “strongly” positive based on degree and timing of the ischemic electrocardiographic response. A positive exercise test was also moderately associated with noncardiovascular mortality; the relative risk for all-cause mortality was 7.2 before and 3.4 after age adjustment. The relative risk for cardiovascular mortality associated with a positive exercise test was not appreciably altered by covariance adjustment for known coronary risk factors other than age. A positive exercise test was a stronger predictor of cardiovascular death than were high plasma levels of low-density lipoprotein cholesterol, low plasma levels of high-density lipoprotein cholesterol, smoking, hyperglycemia, or hypertension. Its impact on risk of cardiovascular death was equivalent to that of a 17.4 year increment in age.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of dopamine on arteries are different depending on the dose, route of administration, and receptor population. Its administration can cause vasodilation by stimulation of dopaminergic receptors, vasoconstriction by stimulation of a-adrenergic and serotonergic receptors, and even spasm of cerebral arteries when given intracisternally in dogs. The ability of dopamine to provoke coronary spasm was assessed in 18 patients with active vasospastic angina in whom this amine was infused at rates of 5, 10, and 15 g.g/kg/min for periods of 5 min each. The 12-lead electrocardiogram and blood pressure (cuff) were monitored throughout the whole test. In nine patients dopamine caused angina and ischemic electrocardiographic changes suggestive of coronary spasm: ST segment elevation in six patients and ST segment depression in the absence of important coronary stenoses in the remaining three. Infusion of dopamine was repeated during coronary angiography in three patients with positive test results; this provoked occlusive coronary spasm with ST segment elevation in two patients and nonocclusive spasm with ST segment depression in the remainder. In conclusion, infusion of dopamine provokes coronary spasm in a sizeable proportion of patients with active vasospastic angina. Its administration may be detrimental in patients susceptible to coronary spasm, such as those with acute myocardial infarction.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Catecholamine-induced triggered activity is thought to be caused by intracellular calcium overload mediated by elevation of intracellular cyclic AMP (cAMP). Although shown to occur in isolated preparations, evidence supporting its clinical existence has been lacking. Electrophysiologic studies were performed in four patients with structurally normal hearts who had exertionally related sustained ventricular tachycardia (VT). Programmed stimulation reproducibly initiated and terminated VT in all patients. Induction of tachycardia was also facilitated by infusion of isoproterenol. Adenosine, an endogenous nucleoside, whose only known electrophysiologic effect on ventricular myocardium and Purkinje fibers is antagonism of catecholamine-induced stimulation of intracellular cAMP production, reproducibly terminated all episodes of VT. The tachycardia was also terminated by intravenous verapamil and by the Valsalva maneuver and/or carotid sinus massage., (-Adrenergic receptor blockade with propranolol either terminated or prevented induction of VT during programmed stimulation or catecholamine challenge. Adenosine was also administered during VT to 14 patients whose arrhythmias fulfilled standard criteria for reentry, two of whom also had exercise-induced VT. Adenosine, at a dose (112.5 to 225, μg/kg iv) sufficient to cause either sinus slowing/arrest or ventriculoatrial block during ventricular pacing, failed to slow or terminate any episode of VT in these patients. Verapamil and autonomic modulation were also ineffective in this group of patients. Adenosine, verapamil, vagal maneuvers (acetylcholine), and, f-adrenergic receptor blockade are all known to decrease the slow-inward calcium current either directly by modulating calcium channels or indirectly by inhibiting production of cellular cAMP. Therefore the observation in this study that interventions that lower intracellular cAMP either terminate or prevent induction of VT in patients with structurally normal hearts and exercise-induced VT suggests that the mechanism of tachycardia may be cAMPmediated triggered activity.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We investigated myocardial 1C-palmitate clearance kinetics at a resting heart rate (control) and during pacing using positron-emission tomography in 10 patients with significant coronary artery stenosis (>70%) and evidence of exercise-induced ischemia. Serial 1C-palmitate images acquired at control and during pacing revealed biexponential myocardial 11C clearance both in myocardium supplied by a stenotic coronary artery (myocardium “at risk”) and in myocardium supplied by a normal coronary artery (normal myocardium). At control, the average rate of myocardial 11C clearance from the early rapid curve component (the clearance half-time) was similar in normal myocardium and in that at risk (22.2 + 5.2 vs 21.0 + 5.4 min, NS), as was the amount of myocardial '`C activity at the end of the early rapid phase (residual fraction 56.3 ± 7.2% vs 54.7 ± 7.3%, NS). Thus, myocardial clearance was homogeneous at control, suggesting a similar rate and amount of 1'C-palmitate oxidation in normal myocardium and in that at risk. Pacing shortened clearance half-times and decreased residual fraction in both normal myocardium and that at risk compared with control. However, clearance halftimes were 17% longer and residual fractions 14% higher in myocardium at risk compared with normal myocardium (p < .005 and p < .01, respectively). Therefore, during pacing myocardial 1'C clearance became heterogeneous, suggesting impaired 11C-palmitate oxidation in myocardium at risk compared with normal myocardium. Increased substrate utilization in response to increased workload can be thought of as a measure of metabolic reserve. Our data suggest metabolic reserve for free fatty acid oxidation is impaired in myocardium supplied by a significantly stenosed coronary artery and that this impairment can be detected by analysis of myocardial 1C-palmitate clearance.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID