Showing papers by "Edward G. Lakatta published in 1989"

Morphological and contractile characteristics of rat cardiac myocytes from maturation to senescence

Abstract: Morphological and contractile characteristics of individual myocytes isolated from rats of 2, 6–9, and 24–25 mo of age were measured. The average myocyte length measured under high power light micr...

Mechanisms of hypertension in the elderly.

Abstract: It has long been recognized that, with advancing age, basal systolic blood pressure increases within the clinically "normal" range in many individuals. Likewise, the prevalence of clinical hypertension, either systolic plus diastolic or isolated systolic, also increases with age. This report reviews the purported mechanisms underlying these types of hypertension and discusses age-associated changes in the cardiovascular system of normotensive individuals that could plausibly interact with these pathophysiologic mechanisms of hypertension.

Chaotic behavior of myocardial cells: possible implications regarding the pathophysiology of heart failure.

Abstract: The heart is a machine designed to pump blood; its duty cycle is the heartbeat. At the cellular level, the essence of a heartbeat is a Ca2+ oscillation (fig. IA): sarcolemmal membrane depolarization (action potential) leads to a transient increase (oscillation) of cytosolic [Ca2+] that causes a transient stiffening and displacement of the contractile filaments leading to cell shortening; subsequent reduction of the cytosolic [Ca2 + ] permits relaxation of the myofilaments and cell relengthening. A fair degree of order among cells is required for normal pump function, that is, effective ejection of blood by the pump and its efficient filling between cycles require that the Ca2+ oscillations that underlie the heartbeat occur and subside uniformly within each cell and relatively synchronously among cells. Recent experimental results and their interpretation have led to a hypothesis of how a single type of disorder among myocardial cells can produce the trilogy of common manifestations of heart failure that results from a variety of etiologies, that is, abnormal diastolic tonus, limited systolic function, and a high probability that arrythmias will occur. This disorder is a spontaneous Ca2 + oscillation that occurs locally within and asynchronously among cells constituting the myocardium.

Physician utilization of laboratory procedures to monitor outpatients with congestive heart failure.

Abstract: • Little is known about how different types of physicians use laboratory procedures in the management of outpatients with congestive heart failure. We therefore analyzed data from a national survey of randomly selected general practitioners, internists, and cardiologists to assess their management of outpatients with New York Heart Association class II congestive heart failure. Most of the 2704 respondents (90%) scheduled office visits between two and four months apart. Body weight, serum electrolytes, and chest roentgenograms were followed regularly by 98% or more of respondents, at median intervals of one to two months, three to five months, and 12 to 17 months, respectively. Serum digoxin levels in patients taking digoxin were followed by 90% of respondents at a median interval of 12 months. Echocardiography, radionuclide ventriculography, and exercise testing were used by fewer respondents (81%, 61%, and 61%, respectively), each at a median interval of 18 months or longer. Cardiologists were significantly more likely to follow patients using either echocardiography, radionuclide ventriculography, or exercise testing. The estimated yearly cost of following a class II congestive heart failure outpatient varied nearly fourfold from the lowest quartile of physicians ($303) to the highest ($1167). Cardiologists were disproportionately represented among the high-cost users. In addition, physicians who were younger or who practiced in an urban setting were significantly more likely to be high-cost users. Thus, simple laboratory tests were used most frequently to follow patients with heart failure, but differences in use of more expensive tests led to large differences in cost. Test use for similar patients is affected by characteristics of both the physician and practice setting. ( Arch Intern Med 1989;149:393-396)

Laser backscatter studies of intracellular Ca2+ oscillations in isolated hearts.

Abstract: We measured intensity fluctuations of 633 nm laser light backscattered from the epicardial surface of isolated, perfused rat and rabbit hearts. Scattered light intensity fluctuations (SLIF) were detected from verapamil-arrested rat hearts. The frequency of SLIF was increased by maneuvers that raise intracellular calcium. SLIF were abolished by removal of extracellular calcium with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and by blockade of sarcoplasmic reticulum calcium release by ryanodine. SLIF were not accompanied by any surface electro-cardiogram and were not abolished by 144 mM extracellular potassium. SLIF were absent in rabbit hearts under base-line conditions but could be provoked by calcium loading using zero potassium and ouabain. We conclude that backscatter SLIF monitor the microscopic motion caused by intracellular calcium oscillations in the intact heart. We measured SLIF from rat hearts during 60 min of global ischemia at 30 degrees C, followed by reflow. Ischemia reduced SLIF frequency to zero within 30 min. Reflow caused an overshoot of SLIF frequency to as much as five times control, suggesting that reflow causes major calcium overload of cells that are at least transiently viable.

Characteristics and Functional Implications of Spontaneous Sarcoplasmic Reticulum-Generated Cytosolic Calcium Oscillations in Myocardial Tissue

Abstract: The process by which electrical excitation of cardiac muscle cells leads to contraction is incompletely understood. It is clear, however, that in all mammalian hearts, release of Ca2+ from the sarcoplasmic reticulum (SR) contributes to the activation of the myofilaments. Spontaneous SR oscillatory Ca2+ release (Fig. 1), given the required conditions, appears to be a universal phenomenon in mammalian preparations (see Lakattaet al., 1985 for review). While spontaneous chaotic cellular contractions, a mechanical sequalae of SR Ca2+ oscillations (CaOsc), was observed over 70 years ago (see Capogrossiet al., 1986b), the universality of CaOsc had not generally been recognized, and its multiple effects on myocardial function have not generally been considered collectively.