Association of acute respiratory symptoms with onset of acute myocardial infarction: Prospective investigation of 150 consecutive patients and matched control patients

Among 150 prospectively investigated patients with acute myocardial infarction (MI) and 150 control patients matched for age, sex and admission date, acute respiratory symptoms occurred in 42 MI patients and in 23 control patients (p < 0.02). Matched-pairs analysis gave an odds ratio for a respiratory syndrome of 2.2:1 for MI. The statistically significant association of minor respiratory syndromes and the onset of MI must be further investigated to determine whether there is any pathogenetic relation of respiratory symptoms, presumably virally induced, to the onset of MI.     

Left ventricular performance during exercise: Response of ear densitogram derivative

The peak derivative of the ear densitogram (PD) has been shown to track left ventricular (LV) function during exercise. Measured as percent change in amplitude from resting control, PD in normal subjects slowly and consistently increased throughout exercise and to 2 minutes of recovery, followed by return to control level. In contrast, PD in patients with coronary artery disease rapidly increased only to 1 minute of exercise, with no significant subsequent increase. Expressed as a percent change from control, the response of normal subjects differs significantly from that of patients with coronary artery disease at 1 and 4 minutes of exercise, and 2 minutes of recovery. The PD increase in normal subjects from end-exercise to 2 minutes of recovery may be attributable to the heart rate decreasing faster than venous return, associated with LV ejection time, which is significantly shorter than heart rate-predicted values 2 minutes after exercise.     

Noninvasive assessment of left ventricular performance in patients with ischemic heart disease: Ear densitographic study during uninterrupted treadmill exercise

Among 738 consecutive patients with chest pain referred for exercise testing, only 17 men fulfilled strict criteria for this pilot study: (1) achievement of at least 90 percent of age-predicted maximal heart rate or etectrocardtographic criteria for a positive test; (2) subsequent coronary anglography; (3) exclusion of prior heart disease; and (4) absence of medication. Measurements of systolic time intervals obtained with ear densitography during early exercise differentiated 10 patients with coronary artery disease (Group 1) from 17 men (7 patients plus 10 normal volunteers) with normal coronary arteries (Group 2). Despite nearly identical heart rate and blood pressure responses In both groups, men In Group 1 had a significantly greater reduction of preelection period (PEP) at 1 minute and 4 minutes as well as a greater decrease hi PEP/LVET (left ventricular ejection time) ratio. Differences were most significant when expressed as percent change of $\text{PEP}\text{LVET}$ ratio from control value (p <0.001 at both 1 minute and 4 minutes). After 4 minutes, men in Group 1 had no further decrease in $\text{PEP}\text{LVET}$ ratio and in 8 of the 10 men $\text{PEP}\text{LVET}$ ratio then increased to peak exercise. By contrast, $\text{PEP}\text{LVET}$ ratio continued to decrease to peak exercise in men In Group 2. The early floor in $\text{PEP}\text{LVET}$ ratio In Group 1 represents limited functional reserve and the subsequent increase suggests functional deterioration. Thus, densHographic systolic time interval measurements during uninterrupted exercise in unmedlcated subjects appear to improve the sensitivity and specificity of the conventional treadmill test.     

The normal and diseased pericardium: Current concepts of pericardial physiology,diagnosis and treatment

The past quarter century has seen remarkable contributions to understanding the role of the pericardium in health and disease and to diagnostic methods in the context of significant changes in the clinical spectrum of acute pericarditis, pericardial effusion and their sequelae. Anatomic studieshave demonstrated pericardial ultrastructure and its relation to function and delineated the pericardial lymphatics and their participation in inflammation and tamponade. Physiologic investigationshave revealed the pericardium's mechanical, membranous and ligamentous functions and its role in ventricular interaction, pericardial modification of cardiac responses during acute cardiocirculatory loading and effects on diastolic function (and, at high filling pressures, systolic function), including reduction by pericardial fluid of true filling pressure—the myocardial transmural pressure. The diastolic mean pressure plateau and phasic venoatrial pressure and flow during cardiac tamponade have been further characterized and the mechanisms producing pulsus paradoxus have been elucidated, including the importance of inspiratory increase in right ventricular filling. A far reaching compensatory response to tamponade has been revealed, particularly adrenergic stimulation, and, over time, blood volume expansion. Right heart tamponade and low pressure tamponade have been identified and the importance of the pericardium in the restrictive dynamics of right ventricular myocardial infarction has been demonstrated. Constrictive pericarditis,And the currently more common effusive-constrictive pericarditis,have been studied, in depth, clinically and hemodynamically.Cardiography in pericardial diseasenow includes M-mode and two-dimensional echographic studies, enabling rapid diagnosis and further physiologic study in cardiac tamponade and constriction. The four stages of typical electrocardiographic evolutionin acute pericarditis and atypical variants have been codified and characteristic PR segment deviations identified. The non-etiologic role of acute pericarditis in arrhythmiashas been clarified in prospective clinical and postmortem investigations. Electric alternation has been elucidated and its relation to cardiac "swinging" has been at least partly explained. Special roles now exist for contrast roentgenography, computed tomography(especially for cysts) and radionuclide imaging. Clinical advancesin pericardial disease include changes in the prevalence of established etiologies and identification of new etiologies, for example, immunopathic processes to explain recurrent pericarditis and the post-injury (including postoperative) pericardial syndromes. New forms of constriction—uremic, postoperative, radiation—have appeared in increasing numbers. The pericardial rubhas been characterized and codified, confirming a typical three-component structure (with frequent exceptions).     

Exercise-induced bundle branch block

Exercise-induced bundle branch block (BBB) is poorly understood. An investigation was made of its clinical, electrocardiographic, coronary angiographic, and myocardial scintigraphic characteristics, with follow-up data in 16 patients, aged 59 ±9 (mean ± standard deviation) years, 11 who had left BBB and 5 who had right BBB. Fourteen had a preexisting baseline electrocardiographic abnormality; 11 had either incomplete BBB or nonspecific intraventricular conduction delay. Heart rates at onset of exercise BBB varied from 70 to 166 beats/min and in 9 patients the rates at BBB onset and offset appeared to be related, occurring within 8 beats/min of each other. Coronary artery disease (CAD) was diagnosed in 10 patients, cardiomyopathy in 2, and probable coronary spasm in 2. One patient had ventricular arrhythmias of uncertain origin, and 1 appeared to have no cardiac disease. Three patients had reversible thallium perfusion defects consistent with ischemia concurrent with developing BBB. The 3 patients in whom exercise BBB persisted all had CAD. Over a mean of 28 months of follow-up, only 1 patient had a morbid cardiac event—nonfatal myocardial infarction—and 2 died from noncardiac causes. Thus, exercise BBB primarily occurs in the context of cardiac disease, most commonly CAD, and concurrent ischemia may be demonstrable; the presence of “rate relation” does not militate against CAD.     

Rate of rise of the carotid pulse: An investigation of observer error in a common clinical measurement

Bedside estimation of the rate of rise of the carotid pulse is a standard clinical observation whose reliability has not been determined. To ascertain interobserver agreement (primary objective) and compare the velocity of rise of the carotid displacement (not pressure) pulse (supplementary objective), three blinded observers evaluated, ranked and palpated the velocity of rise of carotid pulse as “unremarkable,” “slow” or “rapid” in 20 consecutive patients. The relative rate of rise of the recorded carotid pulse was represented by the angle between baseline and the initial carotid peak at a standard paper speed of 100 mm/s.Chi-square analyses yielded no significant interobserver agreements (probability [p] 0.22 to 0.51). There was also no correlation of observers' ranking of rise of carotid pulse with the ranking from independent measurement of the recorded pulse rise velocity (p = 0.10 to 0.99). Observer agreement was unanimous only four times and even in these instances was consistent with the recorded carotid pulse rise velocity only once. The results suggest that unbiased observers cannot reliably discriminate slow from “normal” velocity of rise of carotid pulse.     

Frequency of arrhythmias in acute pericarditis determined by holter monitoring

Twenty-four-hour electrocardiographic monitoring in 49 of 50 consecutive patients with acute pericarditis and sinus rhythm at onset (29 with etiologic or unrelated heart disease) disclosed 4 instances of intermittent supraventricular tachycardia, 2 in patients in whom tamponade developed and 1 in a patient with acute myocardial infarction. Eight other arrhythmias, also nonsustained, occurred exclusively in patients with heart disease. Ectopic beats without other arrhythmia occurred in 10 patients without heart disease, but were infrequent (1 to 30 per hour) in 9. Ectopic beats without other arrhythmias occurred in 19 patients with heart disease but were infrequent in 16. Pericarditis per se does not appear to be a recognizable arrhythmogenic influence. As a corollary, significant rhythm disturbance—particularly continuous-beat arrhythmias—during acute pericarditis implies a cardiac abnormality.     

The randomized controlled clinical trial: Scientific and ethical bases

Randomized controlled trials are increasingly accepted in principle but not always in practice, particularly for surgical therapies. Successful surgical randomized controlled trials demonstrate their feasibility, and reports of uncontrolled surgical trials now commonly bear a statement that a definitive answer requires a controlled trial. Scientifically, the randomized controlled trial is the most powerful way to determine a result ascribable only to the trial treatment. Although randomized controlled trials can be imperfect or improperly conducted, they are designed to circumvent biased behavior by investigators. With candor in informed consent, the equal chance not to get a trial treatment makes the randomized controlled trial the most ethical design. Thus, scientific, behavioral, and ethical cases support the randomized controlled trial as the optimal method for investigation of nearly all therapeutic innovations and as a requirement for publication.     

Elucidation of physiologic lengthening of left ventricular ejection time during early upright exercise

To elucidate the relationship between heart rate (HR) and left ventricular ejection time (LVET) during early exercise, 30 patients with chest pain were studied at 1 (1′) and 4 minutes (4′). Mean results for control → 1′ exercise: HR 79 to 105 beats per minute, LVET 247 to 260 msec. Thus instead of shortening as predicted by the HR change at 1′ of exercise, LVET rose significantly (p < 0.001). Subsequently LVET fell as HR continued rising, and by 4′ had fallen toward control level. This phenomenon is comparable to the paradoxical decline in LVET as HR decreases early post-exercise and is comparably explained by transiently disproportionate change in determinants of LVET, stroke volume, and ejection rate. Absence of difference in response of exercise-positive (ST depression ≥ 1 mm) and exercise-negative patients, also supports this initial paradoxical lengthening in LVET as a physiologic response.