摘要:

The Medical Device Amendments of 1976 gave the Food and Drug Administration (FDA) new authority to regulate all medical devices. This regulation requires that manufacturers provide data supporting the safety and effectiveness of new and modified devices before marketing them, and eventually provide similar data even for devices now on the market. Those working in the cardiovascular field use a device every day of their professional lives; therefore, the Medical Device Amendments will have a significant effect on everyone in the field. We must understand the law so that we can provide scientific guidance to the FDA and to the medical device industry; in this article we aim to provide the necessary information.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

In this study we attempted to determine if the cold pressor test, a known sympathetic reflexogenic stimulus, could precipitate coronary artery spasm. Thirty-five patients undergoing coronary arteriography for evaluation of chest pain syndromes were given the cold pressor test. During 1 minute of cold pressor stimulation, aortic systolic pressure increased 18.1 ± 9.7 mm Hg (mean ± SD) and heart rate did not change significantly. Focal coronary artery spasm was provoked in seven patients, each of whom had an atheromatous plaque at the site of spasm. Four of six patients with a precatheterization clinical diagnosis of variant angina (group 1) had coronary artery spasm, and two of the four had associated ischemic manifestations. Of 14 patients in whom classic angina (group 2) was diagnosed before cardiac catheterization, two manifested focal coronary spasm. One of 15 patients thought to have atypical chest pain (group 3) manifested spasm. There were no significant differences in baseline variables (aortic systolic or diastolic pressure, heart rate, double product and left ventricular end-diastolic pressure) or hemodynamic response (aortic systolic pressure, heart rate or double product) to cold pressor stimulation between patients in each group and between those who manifested spasm and those who did not. Ventricular ectopy and ventricular tachycardia developed in one patient but were readily reversed with intravenous nitroglycerin. Quantitative angiography showed that the luminal diameter of normal coronary segments significantly decreased in each group of patients in response to cold pressor stimulation, but this response was most pronounced in the variant angina group (-12.7 ± 11.5% from control in group 1, −5.1 ± 10.2% in group 2, and −7.9 ± 9.6% in group 3;p< 0.001 for each group). Patients who are prone to coronary spasm may represent one extreme of a spectrum of reactivity to a coronary vasoconstrictive stimulus. The cold pressor test can provoke focal coronary artery spasm in certain patients and may be a useful nonpharmacologic provocative screening test to aid in the diagnosis of this phenomenon.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Eleven men with coronary artery disease were studied to determine whether they would manifest inappropriate coronary vasoconstriction in response to mental stress. Mental stress was induced by having the patient perform difficult mental arithmetic in time with a clicking metronome. Aortic blood pressure and thermodilution coronary sinus blood flow were recorded continuously before and during the mental arithmetic. For the group, heart rate rose from 70 to 82 beats/min, systolic blood pressure rose from 161 to 181 mm Hg and diastolic blood pressure rose from 71 to 78 mm Hg. Coronary resistance decreased by 16%. The index of myocardial oxygen consumption rose by 40%, and there was an equivalent rise in coronary sinus blood flow of 41%, with no change in coronary arteriovenous oxygen difference.Because the increase in myocardial oxygen consumption was accompanied by a proportional increase in coronary sinus blood flow, a decrease in coronary resistance and no change in myocardial oxygen extraction, we conclude that the response of patients with coronary artery disease to at least moderately severe mental stress is not characterized by abnormal coronary vasoconstriction.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The coronary microcirculation was examined for platelet and fibrin thrombi in hearts from 21 normal subjects and 244 cardiac patients, including 168 with ischemic heart disease (IHD) and 76 with other types of heart disease. Seventy-seven cases were sudden cardiac death (SCD). No microthrombi were present in any of the normal hearts, whereas platelet and fibrin thrombi were present in the coronary microcirculation in 32 of 244 cardiac cases (13.1%), including 19 with IHD and 13 with other types of heart disease and after cardiac surgery. The microthrombi were either embolic or represented in situ thrombosis, depending upon the underlying pathologic process. There was no significant difference in the incidence of microthrombi in SCD patients with IHD (10 of 50, 20%) compared with patients who survived longer (nine of 93, 10%). In SCD patients, however, platelet microthrombi were more frequent in patients less than 45 years of age compared with those older than 45 years of age (p = 0.0002). We concluded that corQnary microcirculatory thrombi are not uncommon in heart disease. A subgroup of SCD in young patients with IHD has been identified in whom microcirculatory platelet thrombosis is the main cardiac pathologic process. The significance of this process is emphasized by the associated myocardial damage.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Both microvascular damage and myocardial cell injury occur after coronary occlusion, but the relationship of these two events is unclear; specifically, it is unknown whether microvascular damage causes myocardial cell injury. Dogs were subjected to coronary occlusion for 20, 40, 60, 90 or 180 minutes, after which subendocardial and subepicardial biopsies were obtained for electron and light microscopy of 1-, u sections. Of 312 biopsies of ischemic myocardium, 181 showed myocardial cell injury with no microvascular damage; 131 showed myocardial cell injury and microvascular damage; but none showed microvascular damage without myocardial cell injury. Although ultrastructural evidence of myocardial cell damage was present in the subendocardium after 20-40 minutes of ischemia, ultrastructural evidence of microvascular damage was not prominent until 60-90 minutes after coronary artery occlusion. Morphologic ultrastructural evidence of microvascular damage lagged behind myocardial cell injury, suggesting that ultrastructural microvascular damage is not a primary cause of ultrastructural myocardial cell injury.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The cross-sectional area (the portion enclosed by the internal elastic membrane) of histologic sections from the first 5-mm long segments of the right, left anterior descending and left circumflex coronary arteries was determined by videoplanimetry in 98 necropsy patients with coronary heart disease and in 46 control subjects who did not have significant coronary narrowing. Significant (p< 0.001) differences were observed in the mean cross-sectional area of each of the three major coronary arteries in the subgroups of coronary patients and among and between the control subjects. These differences resulted primarily from differences in heart weight and, to a slight extent, in age. Difference in sex was not significant. The 20 patients with angina pectoris had the smallest coronary arteries (mean cross-sectional area of each of the 60 arteries 6.0 mm2) and the smallest hearts (mean weight 386 g). The 18 patients with healed myocardial infarcts and intractable congestive heart failure had the largest coronary arteries (mean area 8.6 mm2) and the largest hearts (mean weight 588 g). The 23 patients with acute transmural myocardial infarcts and the 19 with sudden coronary death had similar-sized coronary arteries (mean area 7.6 mm2) and similar-sized hearts (mean weight 471 g). The 18 patients with healed myocardial infarcts, subsequently asymptomatic courses and noncardiac deaths had slightly enlarged arteries (mean area 6.9 mm2) and hearts (mean weight 430 g). The 31 control subjects with cancer and normal or near-normal-sized hearts (mean weight 309 g) had the smallest coronary ateries (mean area 5.0 mm2). The 16 controls with aortic valve disease had the largest hearts (mean weight 730 g) and the largest coronary arteries (mean area 9.6 mm2'). When heart weights were equalized (450 g), older patients had larger coronary arteries than younger patients (mean area < 40 years 6.5 mm2, 41-60 years 6.8 mm2and > 60 years 7.6 mm2).

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Patients who survive an acute myocardial infarction (AMI) have significant coronary disease and are at risk for angina pectoris, recurrent myocardial infarction and sudden death. This study provides data gathered prospectively for 106 patients surviving myocardial infarction who had coronary arteriography, left ventriculography and 24-hour electrocardiographic recordings before hospital discharge and were followed 30 months. Univariate analysis showed that low ejection fraction, proximal left anterior descending coronary disease and significant disease in all three coronary arteries were associated with a high risk of sudden cardiac death. The ECG location or type of infarction was not helpful in predicting mortality, reinfarction or continuing angina. Multivariate analysis of 30 clinical and laboratory variables identified previous myocardial infarction and an ejection fraction less than 40% as the best predictors of mortality; all 13 patients who died were identified by these two variables. Three-vessel coronary artery disease, proximal left coronary disease and complicated late hospital-phase ventricular arrhythmias did not provide additional information about mortality once the information provided by the first two variables was considered. Multivariate analysis identified hypertension, three-vessel coronary disease, postinfarction angina pectoris and previous AMI as significant predictors of recurrent AMI during the 30 month follow-up.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

In a double-blind randomized study, 30 mg/kg of methylprednisolone sodium succinate (MPN) or 15 mg/kg of mannitol placebo (PL) were infused in 28 patients after acute myocardial infarction. Measurements were obtained immediately before and for 24 hours after the initial infusion. The partial pressure of oxygen at 50% saturation of hemoglobin (P50,) did not change significantly in vitro or in vivo after MPN, whereas 2,3 diphosphoglycerate (2,3 DPG) increased from 13.2 to 14.2 μmol/g Hb (p < 0.05) in the group receiving PL. The arteriovenous oxygen difference (Ca-vO2) remained constant after MPN or PL. The cardiac index (CI) increased after MPN (p < 0.02) associated with an increase in the oxygen consumption index (CaV 02) from 146 to 170 ml/min/m2(p< 0.05). These data show that MPN increases CI after acute myocardial infarction, but has no specific effects on P50, 2,3 DPG or Ca-vO2.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The purpose of this study was to determine the characteristics and incidence of abrupt occurrence of abnormal initial QRS forces that cannot be explained by acute myocardial infarction or left or right ventricular overload. Computerized data from 3175 patients with suspected acute infarction were reviewed to identify those in whom the ECGs revealed QRS complexes considered to be diagnostic (Q wave or markedly diminished R wave) in the presence of persistently normal profiles of both creatine kinase and lactic dehydrogenase isoenzymes. Lead misplacement had been minimized by obtaining multispace tracings and vectorcardiograms.Eight patients (0.25%) were identified. The abnormal forces were confined to leads V1-3in six, V4-6in one, and involved all precordial leads in the last. These QRS changes resolved completely within 6 days in all eight patients, which suggests that they did not have an acute infarction. This theory was supported by postmortem examination in one patient.An extremely low incidence (0.25%) has been documented for a syndrome characterized by transient loss of initial anterior forces with persistently normal isoenzyme profiles. Although no etiology could be determined, a transient conduction block of the septal fascicle of the left bundle could have been the cause in seven of the eight patients.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

To study recurrent ventricular tachycardia in the late phase of myocardial infarction (MI), transmural anteroapical infarcts were created by ligation of the left anterior descending (LAD) coronary artery in 25 dogs. Twenty dogs survived LAD ligation and underwent an open-chest electrophysiologic study an average of 20 days after MI. Programmed electrical stimulation was carried out using the extrastimulus technique and short bursts of rapid ventricular pacing via bipolar electrodes positioned at multiple left ventricular endocardial sites. Sixteen dogs had electrically induced ventricular tachycardia, and in 11, sustained ventricular tachycardia was reproducibly initiated and terminated by programmed ventricular stimulation. Short bursts of rapid left ventricular pacing from areas in periinfarct zone was the most effective technique for initiating ventricular tachycardia. The electrophysiologic phenomena in this model of sustained ventricular tachycardia in 3-week-old MI included electrically induced changes in rate and morphology and biventricular capture without termination during tachycardia.

ISSN:0009-7322    

出版商:OVID    

年代:1980

数据来源: OVID