Cardiovascular dynamics, blood volumes, renal functions and electrolyte excretions in the same patients during congestive heart failure and after recovery of cardiac compensation

Chronic cardiac reactions. III. Factors involved in the development of structural dilatation

The significance of various factors for the development of structural dilatation in the chronically pressure-loaded and failing heart were evaluated. The investigations were performed on male rats with renal (Goldblatt II) and spontaneous (Aoki-Okamoto) hypertension at different stages of haemodynamic overload. Two groups of SHR were submitted to intermittent feeding (SHR IF); one group received additionally the beta-blocking agent atenolol (50 mg/kg b.w.; SHR IF + beta Bl.). Haemodynamic measurements were carried out under open chest conditions. Myosin isoenzyme pattern, hydroxyproline concentration and circulating blood volume were determined. Transformation to slower myocardium per se, induced by IF, did not lead to significant change in ventricular configuration. After additional blockade of beta-adrenergic receptors there were indications of unfavourable development of left ventricular configuration. Inhibition of hypertrophic mass increase due to curtailed adrenergic stimulation could be an influential factor in the development of dilatation. Further investigations, however, are required to establish the relationship between the adrenergic system, on the one hand, and degree of hypertrophy as well as structural dilatation of the ventricle, on the other hand. The established marked increase in hydroxyproline concentration of the dilated ventricle of SHR in congestive failure is consistent with the assumption of a causal link between the degree of fibrosis and structural dilatation. Observations on rats with aorto-caval shunt and Goldblatt II rats with eccentric hypertrophy and corresponding increase in filling potential or circulating blood volume indicate a correlation between the latter and ventricular size. Thus, we assume that curtailed protein synthesis, fibrosis and regulatory processes related to water and electrolyte balance, but not myocardial transformation per se, play a role in the development of structural dilatation. The relative contribution of each factor, however, may depend on the experimental model that is used.

Cardiac and sinoaortic reflexes during aortic constriction in awake calves

The hemodynamic responses to increased afterload of the left ventricle were studied in conscious calves before and during cooling of the cervical vagus nerves bilaterally. The calves were chronically instrumented to measure (or derive) heart rate, stroke volume, cardiac output, iliac, superior mesenteric and renal flows and resistances, mean aortic, right atrial, pulmonary artery, and left atrial pressures, the systemic and pulmonary pressure gradients, and total systemic and total pulmonary resistances. The calves were also instrumented to produce reversible partial constriction of the ascending aorta and for cooling of the cervical vagus nerves. The hemodynamic responses to increased afterload were characterized before and during bilateral cervical vagus nerve cooling to 6-7 degrees C. Aortic constriction causes stroke volume, cardiac output and aortic pulse pressure to decrease. Left atrial pressure and total peripheral resistance increase. Mean aortic pressure is constant during aortic constriction alone, despite a continued decrease in pulse pressure, due to a balance between sinoaortic reflexes which attempt to increase arterial pressure in response to the decreased pulse pressure and cardiopulmonary reflexes which attempt to decrease arterial pressure in response to the increased left atrial and cardiopulmonary pressures. Vagal cooling removes cardiopulmonary reflex modulation of the sinoaortic reflexes. During aortic constriction and vagal cooling, the carotid sinus reflex, acting alone, causes large increases in renal and total peripheral resistance and mean aortic pressure.

Hemodynamics of high afterload left heart failure for assist device testing

The hemodynamic responses to increased afterload of the left ventricle were studied in conscious calves during exercise. The calves were chronically instrumented to measure (or derive) heart rate, stroke volume, cardiac output, iliac, superior mesenteric and renal flows and resistances, mean carotid, aortic, right atrial, pulmonary artery, and left atrial pressures, the systemic and pulmonary pressure gradients, and total systemic and total pulmonary resistances. The calves were also instrumented to produce reversible partial constriction of the ascending aorta and common carotid arteries and for cooling of the cervical vagus nerves. The hemodynamic responses to increased afterload were characterized during treadmill exercise at 2 mph. These responses were compared to the hemodynamic responses to bilateral carotid artery occlusion with and without vagal cooling.