Showing papers in "American Journal of Cardiology in 1977"

End-systolic pressure/volume ratio: A new index of ventricular contractility☆

Abstract: A thesis recently developed from a series of experiments on the isolated canine left ventricle is described. It is claimed that the ventricular presure/volume ratio at end-systole is relatively insensitive to cardiac loading and varies greatly in response to changes in ventricular contractility. The clinical viability of this basic finding rests on the substitution of diameter for volume in this formulation. Diameter can be measured using a noninvasive ultrasonic technique in the clinic. Accordingly, end-systolic pressure/diameter ratio was studied in the isolated preparation and found to be similarly insensitive to loading conditions and sensitive to inotropic interventions. A further analysis of the pressure/diameter ratio in the ventricle of the conscious dog is in progress. In parallel with these studies, use of the pressure/diameter ratio to evaluate contractility in cardiac patients is being tested. The preliminary findings from conscious dogs and clinic patients are briefly discussed.

Transient Asymptomatic S-T Segment Depression During Daily Activity

Abstract: The significance of asymptomatic episodes of ischemic type S-T segment depression was studied in 20 patients with coronary heart disease. Continuous 10 hour electrocardiographic recordings accompanied by detailed daily diaries of activity and symptoms were obtained periodically during a mean time of 16 months. All patients had ischemic type S-T depression associated with angina pectoris during treadmill exercise. Measurements of heart rate, S-T depression and exercise level at the onset of angina obtained during repeated controlled exercise tests at the start of each study period were compared with the measurements recorded during daily activity. After 2,826 hours of recording, 411 transient epidsodes of ischemic type S-T depression were noted during usual daily activity. Only 101 (25 percent) of these episodes were associated with angina. The remaining episodes were unrelated to other symptoms or to posture. All occurred at heart rates significantly lower than those observed at the onset of angina during exercise testing. Of these episodes of asymptomatic S-T depression, 72 percent occurred only at rest or during very light activity such as slow walking or sitting. Nitroglycerin administered hourly significantly reduced the frequency of these episodes, thus supporting the concept that they represent painless ischemia. Because the episodes of asymptomatic ischemic type S-T depression occurred more frequently than angina during usual daily activity and were evident at heart rates and activity levels well below those expected to evoke ischemia, they may be caused by factors other than those that cause angina.

Arrhythmias documented by 24 hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease.

Abstract: Results are reported of portable 24 hour dynamic electrocardiographic monitoring in 50 male medical students without cardiovascular disease, as defined by normal clinical and noninvasive cardiovascular examination. During waking periods, maximal sinus rates ranged from 107 to 180 beats/min (mean ± standard deviation 141 ± 17) and minimal rates from 37 to 65 beats/min (mean 53 ± 6). Maximal and minimal observed sleeping rates were, respectively, 70 to 115 (mean 86 ± 9) and 33 to 55 (mean 43 ± 5). Twenty-five subjects (50 percent) had episodes of marked sinus arrhythmia as defined by spontaneous changes in adjacent cycle lengths of 100 percent or more. Fourteen subjects (28 percent) had sinus pauses of more than 1.75 seconds, usually during sinus arrhythmia. Transient nocturnal type I second degree atrioventricular (A-V) block was noted in three subjects (6 percent). Of 28 patients (56 percent) having atrial premature beats, only 1 (2 percent) had more than 100 such beats (141) in 24 hours. Of 25 patients (50 percent) having premature ventricular contractions, only 1 (2 percent) had more than 50 such contractions (86) in 24 hours. In conclusion, frequent atrial and ventricular premature beats are unusual in a young adult male population. In contrast, bradyarrhythmias (including marked sinus arrhythmia with sinus pauses, sinus bradycardia and nocturnal A-V block) are common. These findings are useful in evaluating the clinical significance of arrhythmias detected with portable monitoring.

Histologic changes in the normal aging aorta: Implications for dissecting aortic aneurysm

Abstract: The histologic changes that occur in the media of the normal aorta at various ages were studied in 100 normal aortas. These changes encompassed (1) cystic medial necrosis, defined as pooling of mucoid material; (2) elastin fragmentation, characterized by disruption of elastin lamellae; (3) fibrosis, defined as an increase in collagen at the expense of smooth muscle cells; and (4) medionecrosis, defined as areas with apparent loss of nuclei. The changes showed a striking correlation with age and may represent the normal aging process for the aorta as determined histologically. The alterations showed a close relation in onset and location within the media, suggesting a phenomenon of injury and repair caused by hemodynamic events. These findings in the normal aging aorta reveal that none of the histologic changes observed can be regarded as the specific structural alteration responsible for the development of dissecting aneurysm.

Epidemiologic studies of coronary heart disease and stroke in Japanese men living in Japan, Hawaii and California: Incidence of myocardial infarction and death from coronary heart disease

Abstract: The incidence of myocardial infarction and death from coronary heart disease was studied in defined samples of 45 to 68 year old Japanese men in Japan, Hawaii and California. The incidence rate was lowest in Japan where it was half that observed in Hawaii (P less than 0.01). The youngest men in the sample in Japan were at particularly low risk. The incidence among Japanese men in California was nearly 50 percent greater than that of Japanese in Hawaii (P less than 0.05). A striking increase in the incidence of myocardial infarction appears to have occurred in the Japanese who migrated to the United States; this increase is more pronounced in California than in Hawaii.

Ischemic contracture of the myocardium: mechanisms and prevention.

Abstract: Ischemic contracture of the left ventricle (“stone heart”) occurs in the rat heart after a period of global ischemia at 37° C. The time of onset of contracture can be delayed by various interventions that reduce myocardial energy demand, increase myocardial energy supply or reduce cellular calcium influx. Conversely, the time of onset of contracture may be advanced by interventions that reduce the energy supply. Analysis of myocardial energy metabolism, and particularly of adenosine triphosphate (ATP) availability in relation to the onset and duration of contracture suggests that contracture is initiated when the cellular ATP content decreases to approximately 12 μmoles/g dry weight. Furthermore, the progression of contracture is characterized by an acceleration in the rate of ATP degradation and the completion of contracture coincides with the reduction of ATP to 3 to 4 μmoles/g dry weight. The results of this study suggest that the development of ischemic contracture represents the accumulation of rigor complexes arising as a result of an ATP deficiency. These rigor complexes are able to exacerbate the contracture by promoting uncontrolled ATP hydrolysis. Although the development of these complexes and the onset of contracture is calcium-insensitive the results indicate that calcium availability may influence the magnitude of the developed contracture.

Correlative classification of clinical and hemodynamic function after acute myocardial infarction

Abstract: To characterize the relation between clinical and hemodynamic state in acute myocardial infarction, 200 patients with acute infarction were evaluated with clinical and hemodynamic criteria. Patients were classified clinically on the basis of peripheral hypoperfusion (hypotension, tachycardia, confusion, cyanosis, oliguria) and pulmonary congestion (rales, abnormal chest roentgenogram). Four clinical subsets were defined that correlated with cardiac index (Cl, liters/min per m2) and pulmonary capillary pressure (PCP, mm Hg): (see article). Parallel hemodynamic subsets were developed independently on the basis of depressed cardiac index (2.2 liters/min per m2 or less) and elevated pulmonary capillary pressure (greater than 18 mm Hg). The rate of accuracy of clinical examination in predicting hemodynamic abnormalities was 83 percent. Mortality rates were similar in the clinical and hemodynamic subset calssifications, averaging 2.2 percent in subset I, 10.1 percent in subset II, 22.4 percent in subset III and 55.5 percent in subset IV. Drug interventions in the course of hospitalization resulted in a 38 percent increase in depressed cardiac index and 34 percent decrease in elevated pulmonary capillary pressure. Resolution of clinical abnormalities paralleled this hemodynamic improvement in 70 percent of patients. These data suggest that clinical performance and both clinical and hemodynamic subsets are directly relevant to establishing prognosis and the selection of therapy in patients with acute myocardial infarction.

Relation of body weight to development of ischemic heart disease in a cohort of young north American men after a 26 year observation period: The manitoba study

Abstract: The role of overweight as a risk factor for ischemic heart disease remains controversial. Therefore, in the Manitoba Study of a cohort of 3,983 men with a mean age at entry of 30.8 years, initial measurements of body weight, represented by body mass index (weight/height 2 ), were compared with the 26 year incidence of ischemic heart disease. After adjustment for the effects of age and blood pressure in univariate and multivariate analysis, body mass index was a significant predictor of the 390 cases of ischemic heart disease. To elucidate this relation further, the cohort was further analyzed after categorization by age at entry, time of occurrence of disease after entry and manifestation of ischemic heart disease. The association with weight was most apparent in men less than 40 years of age and was not evident until 16 years of follow-up. A high body mass index was significantly associated with development of myocardial infarction, sudden death and coronary insufficiency or suspected myocardial infarction; the relation was strongest with sudden death. Among men who had a myocardial infarction, body mass index was more strongly associated with sudden death and was the best predictor of myocardial infarction occurring after 20 years of observation. Thus, after adjustment for the effect of age and blood pressure, overweight is a definite risk factor but primarily in younger men, after long periods of observation and for certain manifestations of ischemic heart disease.

Provocation of coronary spasm with ergonovine maleate: New test with results in 57 patients undergoing coronary arteriography☆

Abstract: Ergonovine maleate (Ergotrate) was given to 57 patients undergoing coronary arteriography for investigation of angina occurring at rest or without provocation when routine study showed normal arteries or insufficient occlusive disease to explain their symptoms. This provocative test induced coronary arterial spasm in 13 patients, 10 of whom had definite Prinzmetal's angina. The spasm was easily reversed with sublingually administered nitroglycerin. The spasm was occlusive or nearly occlusive in nine patients, and there was associated reproduction of the chest pain and S-T elevation similar to the spontaneous episodes. One patient with Prinzmetal's angina had S-T depression rather than elevation in association with the chest pain. The other three patients without Prinzmetal's angina had focal narrowing without coronary occlusion, reproduction of the chest pain or electrocardiographic changes. Of the 44 patients who did not demonstrate coronary spasm in response to ergonovine, 29 had normal coronary arteries and 15 had various degrees of atherosclerotic occlusive disease. We conclude that cautious administration of ergonovine maleate during coronary arteriography can be safely used to elicit coronary spasm in some patients who have insufficient fixed occlusive disease to explain their symptoms.

Pathophysiologic assessment of hypertensive heart disease with echocardiography

Abstract: Assessment of the pathophysiologic changes associated with systemic hypertension has been limited by difficulty in justifying invasive studies of the left ventricle. Echocardiography, because it is noninvasive, offers an attractive method of assessing cardiac dimensions and function in hypertensive heart disease. Fourteen age-matched normotensive subjects and 31 patients with hypertension (but without clinical evidence of coronary artery disease) were studied before receiving any antihypertensive therapy. The patients with hypertension were classified into three groups on the basis of previously established electrocardiographic and chest X-ray criteria: group I, normal electrocardiogram and chest roentgenogram (13 patients); group II, left atrial abnormality by electrocardiogram and a normal chest roentgenogram (8 patients); and group III, left ventricular hypertrophy by electrocardiogram or chest roentgenogram, or both (10 patients). Mean arterial pressure increased significantly from group I to group II and from group II to group III ( P P P P P P P

Neural and psychologic mechanisms and the problem of sudden cardiac death

Abstract: Brain stimulation can provoke a variety of arrhythmias and lower the ventricular vulnerable threshold. In the animal with acute myocardial ischemia such stimuli suffice to provoke ventricular fibrillation. Vagal neural traffic or adrenal catecholamines are not the conduits for this brain-heart linkage. Accompanying increases in heart rate or blood pressure are not prerequisites for the changes in cardiac excitability. Increased sympathetic activity, whether induced by neural or neurohumoral action, predisposes the heart to ventricular fibrillation. Protection can be achieved with surgical and pharmacologic denervation or reflex reduction in sympathetic tone. With acute myocardial ischemia, augmented sympathetic activity accounts for the early surge of ectopic activity frequently precipitating ventricular fibrillation. Asymmetries in sympathetic neural discharge may also contribute to the genesis of serious arrhythmias. The vagus nerve, through its muscarinic action, exerts an indirect effect on cardiac vulnerability, the consequence of annulment of concomitant adrenergic influence, rather than of any direct cholinergic action on the ventricles. There exist anatomic, physiologic as well as molecular bases for such interactions. Available experimental evidence indicates that environmental stresses of diverse types can injure the heart, lower the threshold of cardiac vulnerability to ventricular fibrillation and, in the animal with coronary occlusion, provoke potentially malignant ventricular arrhythmias. Available evidence indicates that in man, as in the experimental animal, administration of catecholamines can induce ventricular arrhythmia, whereas vagal activity exerts an opposite effect. Furthermore, in certain subjects diverse stresses and various psychologic states provoke ventricular ectopic activity.

Pathogenesis of dissecting aneurysm of aorta: Comparative histopathologic study of significance of medial changes

Abstract: In a previous investigation of the normal aging aorta, the claimed specificity of alterations in the media in the pathogenesis of dissecting aneurysm of the aorta was challenged The concept was promoted that these changes are nonspecific and caused by general hemodynamic events within the aorta In this investigation the aortic media was studied in patients with a dilated ascending aorta, whose hemodynamic profile is known to be altered The results were compared with data obtained from the study of aortas with complete or incomplete dissection and aortas from patients with Marfan's syndrome, a condition known to predispose to dissection Only quantitative differences were found between the normal “aging” aorta and the overtly abnormal aorta The pathogenesis of dissecting aneurysm, therefore, is considered to be initiated by processes of injury and repair within the aortic wall, consequent to hemodynamic forces The histologic features of the media previously implicated as the specific underlying defect appear to represent the morphologic substrate of this traumatizing and reparative process This process may gradually lead to dilatation of the aorta and, according to Laplace's law, a vicious cycle may ensue that may lead to further complications Local circumstances determine whether a dilated aorta will rupture or whether an incomplete or complete dissection will occur The fact that the aorta in patients with Marfan's syndrome shows basically the same structural alterations supports the concept proposed The underlying connective tissue disorder in these patients will lead to complications at an earlier age Dissecting aneurysm therefore is part of a spectrum of lesions that have as a common denominator the process of injury and repair

Influence of etiology of atrial fibrillation on incidence of systemic embolism.

Abstract: Atrial fibrillation is well known to increase greatly the risk of systemic arterial embolism in patients with mitral valve disease. In light of the clinical frequency of embolism in patients with atrial fibrillation due to other types of heart disease, a study was made of embolic occurrences in 333 autopsy patients with atrial fibrillation associated with various kinds of heart disease. Considering only symptomatic emboli with pathologic or surgical confirmation, embolism occurred in 41% of patients with mitral valve disease, 35% of those with ischemic heart disease, 35% of those with coexisting mitral and ischemic heart disease and 17% of those with "other" types of heart disease. Embolism was found in only 7% of a control group of 58 autopsy patients with ischemic heart disease without atrial fibrillation. These findings suggest a high risk of embolism from atrial fibrillation of any origin, but particularly from that caused by ischemic heart disease and mitral valve disease.

Electrocardiographic left atrial enlargement. Electrophysiologic, echocardiographic and hemodynamic correlates.

Abstract: The mechanism of the electrocardiographic pattern termed left atrial enlargement was evaluated in 21 patients. Left atrial size and pressure as well as interatrial conduction were correlated with electrocardiographic left atrial enlargement using echocardiography, mean pulmonary capillary wedge pressure and activation time from the P wave to the coronary sinus. In the group as a whole only prolongation of interatrial conduction time was consistently related to the electrocardiographic pattern of left atrial enlargement; left atrial size or pressure was not predictably abnormal in patients with this pattern. Five patients had neither elevation of pulmonary capillary wedge pressure nor echocardiographic evidence of an enlarged left atrium. When the etiologic type of heart disease was analyzed, an enlarged left atrium correlated with electrocardiographic left atrial enlargement only in patients with rheumatic mitral valve disease (eight of nine patients). Elevated pulmonary capillary wedge pressure correlated with electrocardiographic left atrial enlargement in all four patients with cardiomyopathy. In patients with coronary artery disease the electrocardiographic pattern was unrelated to either left atrial pressure or volume overload. Thus, the electrocardiographic pattern termed left atrial enlargement appears to represent an interatrial conduction defect that can be produced by a variety of factors.

Atrial fibrillation in the preexcitation syndrome

Abstract: One hundred patients with proved accessory pathways of the Kent bundle type were studied with multiple intracardiac catheters. During the procedure 16 had atrial fibrillation. Two patterns of induction of atrial fibrillation were noted. In most patients an earlier than expected atrial deflection appeared in one of the atrial recordings and was followed by atrial flutter (cycle length less than 220 msec) or atrial fibrillation either immediately or after a brief period of acceleration of atrial rate. In a few patients, intraatrial conduction delay, manifested as 2:1 block or Wenckebach block from the right to the left atrium or vice versa, occurred before the onset of atrial fibrillation. The incidence of atrial fibrillation was not statistically related to any associated cardiac abnormalities. A significantly large incidence of ventricular fibrillation was recorded in patients who had documented atrial fibrillation either before admission or during the catheter study.

Congenital bicuspid aortic valve after age 20

Abstract: The bicuspid aortic valve is recognized as a frequent cause of aortic stenosis in adults. Aortic stenosis has been reported to occur in as many as 72 percent of adults with a congenital bicuspid aortic valve, with peak incidence occurring in the 5th and 6th decades of life. Review of the clinical records of 152 patients aged 20 years and older found to have a bicuspid aortic valve at autopsy revealed aortic stenosis in only 28 percent. The incidence of aortic stenosis increased progressively with age; 46 percent of patients over age 50 years and 73 percent over age 70 years had some degree of stenosis. The stenotic valves were obstructed by nodular, calcareous masses but commissural fusion was present in only eight cases. The largest group of patients in the series (40 percent) died of infective endocarditis; 77 percent of these were under age 50 years. Primary aortic regurgitation without infective endocarditis was uncommon. Thirty-two percent of the patients in this series had an apparently normally functioning aortic valve, and this rate remained relatively constant with increasing age; 37 percent of patients over age 50 years and 27 percent over age 70 years had an apparently normal valve. The bicuspid aortic valve in patients over age 20 does not invariably become stenotic or insufficient.

Aortocoronary bypass saphenous vein graft atherosclerosis. Anatomic study of 99 vein grafts from normal and hyperlipoproteinemic patients up to 75 months postoperatively.

Abstract: In this anatomic study of 99 saphenous vein grafts recovered at autopsy from 55 patients who survived aortocoronary bypass for 0 to 75 months, a comparison was made between patients with normal and elevated lipid levels in regard to the severity of vein graft intimai proliferation and the prevalence of true atherosclerosis. Although progression of intimai proliferation with time occurred in both patient groups, a greater proportion of hyperlipemic patients had high grade luminal narrowing of vein grafts as the interval after aortocoronary bypass increased. True atherosclerosis did not develop before 12 months in any of the 59 vein grafts from the 27 normolipemic and 5 hyperlipemic patients who survived aortocoronary bypass, but it occurred in 3 of 26 vein grafts (11.5 percent) from normolipemic and 11 of 14 vein grafts (78.6 percent) from hyperlipemic patients who survived 13 to 75 months after aortocoronary bypass. The observation that microscopic changes of atherosclerosis may occur in saphenous vein grafts in some patients without hyperlipemia also emphasizes the importance of effective control not only of blood lipids but also of the other recognized risk factors for atherosclerosis.

Cardiac rupture--challenge in diagnosis and management.

Abstract: Previous studies of the incidence, natural history, pathogenesis and diagnosis of cardiac rupture are presented, and 20 additional cases described. Progressive cardiorrhexis after myocardial infarction causes death in possibly more than 25,000 persons a year in the United States, and more frequent antemortem diagnosis is needed. Suggestions for future clinical and experimental studies are described and possible means of early diagnosis and therapy are outlined.

Management of patients with malignant ventricular arrhythmias.

Abstract: The patient with recurrent malignant ventricular arrhythmias (ventricular fibrillation or ventricular tachycardia with syncope) presents a complex therapeutic problem. To examine this problem, a study was made of 43 consecutive patients with such arrhythmias (mean age 54 years for the 33 men and 43 years for the 10 women). Arrhythmias were not precipitated by either remediable clinical conditions or acute myocardial infarction. The population was divided into two nonrandomized groups based on the type of therapeutic intervention employed. The 26 patients in Group 1 (20 with ventricular fibrillation, 6 with ventricular tachycardia) were subjected to a systematic attempt to select two independently effective antiarrhythmic drugs. Acute drug testing was followed by drug usage over 48 to 72 hours with drug efficacy determined with use of ambulatory monitoring and exercise stress. The 17 patients in Group 2 (10 with ventricular fibrillation, 7 with ventricular tachycardia) received standard antiarrhythmic therapy based on clinical factors and "therapeutic" blood drug concentrations. Twenty-four of 26 patients in Group 1 (92 percent) demonstrated control of arrhythmias and are alive at a mean follow-up period of 17 months. Of 121 drug tests, 47 (39 percent) were effective, 58 (48 percent) were ineffective and 16 (13 percent) provoked major adverse effects. The most effective combination of drugs involved a beta adrenergic blocking agent, a cardiac glycoside and quinldine. Ten of 17 patients in Group 2 (59 percent) have died after a mean follow-up period of 14.8 months. Elements of a successful management program are outlined.

Persistent truncus arteriosus. A study of 66 autopsy cases with special reference to definition and morphogenesis.

Abstract: Sixty-six hearts were examined in which a single arterial trunk, leaving the base of the heart through a single semilunar valve, supplied the aorta, pulmonary artery and coronary arteries. Careful attention was paid to the infundibular morphologic features in these hearts, and these were compared with findings in 24 hearts with single aortic trunk, pulmonary atresia and ventricular septal defect. It was concluded that the two anomalies represented morphologically discrete conditions. This was particularly true with regard to the disposition of the infundibular septum, the ventriculo-infundibular fold and the relation of the coronary arteries to the semilunar sinuses. Although it is theoretically possible for a heart with true persistent truncus arteriosus to have absence of the pulmonary trunk and right and left pulmonary arteries, it is argued that such hearts (“truncus type IV”) are best classified as pulmonary atresia with ventricular septal defect. It is also argued that hearts with a common arterial trunk supplied through discrete ventricular outflow tracts and two semilunar valves are best considered examples of aorticopulmonary window. It is suggested that persistent truncus arteriosus is best defined as that condition in which a single arterial trunk leaves the heart through a single semilunar valve and supplies the aorta, one or both pulmonary arteries and the coronary arteries.

Early changes in regional and global left ventricular function induced by graded reductions in regional coronary perfusion

Abstract: To determine the sequence of changes in segmental myocardial function, regional lactate metabolism and global left ventricular function induced by mild regional ischemia, blood flow in the left anterior descending coronary artery of 10 dogs was reduced by 10 percent decrements with use of a screw clamp. At each level of flow, segmental mechanical function and regional metabolism were assessed, the former with use of a mercury-in-Silastic length gauge and the latter with transmyocardial lactate balance measurements obtained with sampling from the anterior interventricular vein. Coronary arterial flow at the onset of regional lactate production was 48 ± 4 percent (mean ± standard error of the mean) of the control value. The onset of segmental mechanical dysfunction coincided with the onset of lactate production. Epicardial S-T segment abnormalities over the ischemic zone usually could not be detected until coronary flow was further reduced. After the onset of regional ischemia there was a linear correlation between coronary arterial flow and regional lactate production. At the onset of mild regional ischemia, defined as the onset of regional lactate production, no significant or directionally consistent changes were noted in standard measurements of global left ventricular performance, including heart rate, mean aortic pressure, left ventricular end-diastolic pressure, cardiac output, stroke volume, stroke work and peak positive dP/dt (maximal rate of rise of pressure). However, peak negative dP/dt (maximal rate of pressure decrease) decreased from 99 ± 2 to 89 ± 3 percent of the control value ( P

Effect of drugs on conduction delay and incidence of ventricular arrhythmias induced by acute coronary occlusion in dogs

Abstract: The effects of various drugs on delayed activation of the ischemic myocardium and the incidence of ventricular arrhythmias were studied in 34 open-chest anesthetized dogs. The left anterior descending coronary artery was occluded for 6 minutes before and 6 minutes and 42 minutes after administration of aprindine (2.85 mg/kg body weight), quinidine (8 mg/kg) and verapamil (0.2 mg/kg) and during infusion of isoproterenol (0.2 μ g/min). The time intervals from the onset of the QRS complex to the major deflection of the bipolar electrograms recorded within the normal and ischemic zones were measured at cycle lengths of 500, 400 and 300 msec and were correlated with the development of ventricular arrhythmias. At a cycle length of 500 msec, aprindine increased by 19.5 msec the delay in activation time produced by coronary ligation alone ( P P

Epidemiologic studies of coronary heart disease and stroke in Japanese men living in Japan, Hawaii and California: Coronary heart disease risk factors in Japan and Hawaii

Abstract: Various risk factors were evaluated to explain a significantly greater incidence of coronary heart disease in men of Japanese ancestry resident in Hawaii compared with men resident in Japan. The independent predictors of incidence of coronary heart disease in both Japan and Hawaii were systolic blood pressure, serum cholesterol, relative weight and age. These factors appeared to influence incidence similarly in both areas because in each case the correlation coefficients for Japan and Hawaii did not differ significantly. The hypothesis that the greater incidence in Hawaii could be attributed to differences in levels of these risk factors was tested with the Walker-Duncan method. The four variable multiple logistic function describing the probability of coronary heart disease in Japan was applied to the cohort characteristics observed in Hawaii. The estimated incidence thus obtained was not significantly different from that actually observed in the men resident in Hawaii. Therefore the increased coronary risk profile in Hawaii compared with Japan can account for the greater incidence of coronary heart disease in the former. Current cigarette smoking was significantly related to the risk of coronary heart disease in Hawaii but not in Japan. This difference requires further investigation.

TQ-ST segment mapping: critical review and analysis of current concepts.

Abstract: Controversy and confusion surround many aspects of TQ-ST segment mapping today. Technical standards pertaining to the recording and measurement of the TQ-ST deflection have not been uniformly established nor has the correlative value of the deflection as an indicator of myocardial injury been clearly ascertained. The TQ-ST deflection is believed to originate primarily although not exclusively as a result of extracellular potassium accumulation in the ischemic region and subsequent establishment of a transmembrane potential gradient during diastole and systole at the ischemic boundary. Nonspatial factors (including electrolytes, antiarrhythmic agents, heart rate) influence the TQ-ST deflection by altering this gradient. Spatial factors (including ischemic area and shape, electrode location) alter the relative position of the ischemic boundary to the electrode site and as such can be analyzed with the solid angle theorem. Further study of the complex behavior of the TQ-ST segment deflection, particularly in the presence of pharmacologic intervention, is necessary before mapping techniques can be used reliably in clinical studies designed to quantitate and modify ischemic damage.

Postextrasystolic Potentiation as a Predictor of Potential Myocardial Viability: Preoperative Analyses Compared With Studies After Coronary Bypass Surgery

Abstract: The ability to predict reversibility of ventricular dysfunction should be important in determining operability. This study examined the usefulness of postextrasystolic potentiation as such a predictor. Left ventricular wall motion was studied using cineventriculography in 31 patients before and after revascularization surgery. Preoperative ejection fraction and wall motion were analyzed during a sinus beat and after a random ventricular extrasystole, whereas postoperative ejection fraction and wall motion were examined only during a sinus beat. Changes in ventricular motion were correlated with changes in vascular supply achieved by operation. Of the 7 patients whose ejection fraction was improved postoperatively, 6 had shown postextrasystolic potentiation compared with only 10 of the 24 patients without such improvement ( P P

Mechanism of early “pump” failure of the ischemic heart: Possible role of adenosine triphosphate depletion and inorganic phosphate accumulation

Abstract: A marked reduction in oxygen tension and adenosine triphosphate (ATP) content accompanies the early "pump" failure of the ischemic heart. However, it appears to be unlikely that decreased ATP supplies for energy-consuming reactions in the myocardial cell cause the observed decrease in myocardial contractility because of the high ATP-affinity of the substrate-binding sites of known energy-consuming reactions in the heart. Furthermore, lack of chemical energy for the contractile proteins and known ion pumps would tend to promote rigor and not a decrease in contractility. Recent evidence suggests that ATP at concentrations greater than those needed to saturate the substrate-binding sites of energy-consuming reactions can exert modulatory effects on ion fluxes. These modulatory effects of ATP could allow a less severe decrease in ATP concentration to inhibit both calcium entry into the myocardial cell and calcium efflux from the sarcoplasmic reticulum. In addition, the large amounts of phosphate liberated from phosphocreatine and ATP could, by causing formation of insoluble calcium-phosphate precipitates, trap calcium in the sarcoplasmic reticulum and mitochondria in the ischemic myocardium. These proposed explanations for the early "pump" failure in the ischemic heart, together with other theories such as intracell acidosis, appear to warrant further study.

Effects of dobutamine in patients with acute myocardial infarction.

Abstract: This study was designed to evaluate the effects of dobutamine, a new cardioselective beta adrenergic agonist, on cardiac performance and myocardial injury in patients with evolving myocardial infarction. Results in 16 patients given dobutamine (1 to 40 microng/kg per min for 24 hours) were compared with those in two groups of control patients: one of 16 patients matched for predicted infarct size, and the other of 16 patients matched for early ventricular dysrhythmia, analyzed by computer. Infarct size was predicted from plasma creatine kinase (CK) values during the first 7 hours after the initial elevation, before infusion of dobutamine. Overall observed infarct size was estimated from hourly CK values for 48 hours (including those before and after administration of dobutamine). In all patients technetium-99m (stannous) pyrophosphate scans were positive for myocardial infarction. Dobutamine increased cardiac output (assessed by thermodilution) from 4.9 +/- 0.37 (mean +/- standard error) to 6.0 +/- 0.38 liters/min (P less than 0.05) and decreased pulmonary arterial occlusive pressure from 21.5 +/- 2.7 to 16.7 +/- 1.6 mmHg (P less than 0.01) without significantly altering heart rate or systemic arterial blood pressure. The ratio of observed to predicted infarct size, the frequency of independently detected reinfarction or extension of infarction and the frequency of premature ventricular complexes were similar in control and treated patients. Thus administration of dobutamine in doses sufficient to improve ventricular performance after myocardial infarction does not exacerbate myocardial injury or ventricular dysrhythmia.

Significance of subendocardial S-T segment elevation caused by coronary stenosis in the dog: Epicardial S-T segment depression, local ischemia and subsequent necrosis

Abstract: A model of partial thickness ischemia has been developed using subendocardial S-T elevation without epicardial S-T elevation to detect partial thickness ischemia which is sufficient to cause subsequent necrosis. Subendocardial blood flow in this model (measured with radioactive microsphere techniques) may be reduced to 25 percent of normal (P < 0.001) by coronary stenosis and tachycardia while subepicardial flow remains normal. Epicardial S-T depression seems to indicate reciprocally subendocardial S-T elevation as long as a layer of nonischemic epicardial muscle is present, but when ischemia becomes transmural, epicardial S-T elevation occurs. Regional pressure-flow relations were determined as distal coronary pressure was reduced at a constant aortic pressure, heart rate and cardiac output. These relations revealed remarkably effective autoregulation of epicardial blood flow concomitant with progressive subendocardial ischemia.

Effect of Procainamide, Propranolol and Verapamil on Mechanism of Tachycardia in Patients With Chronic Recurrent Ventricular Tachycardia

Abstract: The effect of short-term intravenous administration of procainamide (12 patients), propranolol (4 patients) and verapamil (4 patients) was studied in 12 patients with chronic recurrent sustained ventricular tachycardia. In all patients tachycardia could reproducibly be initiated and terminated with programmed electrical stimulation of the heart. Procainamide (1) lengthened the effective refractory period of the right ventricle, (2) affected the tachycardia zone, (3) reduced ventricular rate during tachycardia, and (4) lengthened the interval between the tachycardia-initiating premature ventricular beat and the first QRS complex of tachycardia. No effect on the refractory period of the right ventricle or the mechanism of tachycardia was seen after administration of propranolol or verapamil. Apart from their therapeutic implications these data suggest that it may be possible to use drugs to study mechanisms of ventricular tachycardia in the human heart.

Structural changes in porcine xenografts used as substitute cardiac valves: Gross and histologic observations in 51 glutaraldehyde-preserved Hancock valves in 41 patients

Abstract: Gross and histologic changes are described in 51 Hancock glutaraldehyde-preserved porcine heterograft bioprostheses from 41 patients: 33 valves from 25 patients had been in place for less than 2 months (“early”) and 18 valves from 17 patients were examined at later periods up to 75 months (“late”) after implantation. The major gross changes were thrombosis (five bioprostheses) and degeneration (three bioprotheses) of the cusps. Major histologic changes observed in 44 bioprostheses (26 early and 18 late) examined histologically were: (1) fibrin deposits on inflow and outflow surfaces of the cusps; (2) inflammatory cell infiltrates; (3) histiocyte deposition; (4) giant cell formation, and (5) focal disruption of the fibrocollagenous structure of the cusps. These observations indicate that porcine bioprostheses are not biologically inert in the human circulation. However, valve failure is rare at the implantation periods studied.