Reserpine: effect on structure of heart muscle.

We examined the ultrastructure of hearts from dogs given reserpine intramuscularly for 4 days, and from untreated dogs. Sections of the myocardium from treated dogs invariably revealed mitochondrial abnormalities at the 5th and 14th days. These included fragmentation and loss of structure of the cristae, and cyst formation. The appearance at 25 days in the treated as well as in all the untreated dogs was normal. We concluded that reserpine in the dose used produces marked structural changes in the mitochondria of heart muscle, and that these changes are reversible. These changes may account for the myocardial depression sometimes seen after administration of reserpine.

Embolization of a left atrial ball thrombus during transesophageal echocardiography.

We report a case of systemic embolization of a left atrial ball thrombus during transesophageal echocardiography (TEE). A 49-year-old man with rheumatic mitral stenosis and atrial fibrillation underwent TEE to evaluate a transient cerebral ischemic attack. TEE demonstrated a free-floating left atrial thrombus. Disappearance of the thrombus during the study occurred after tachycardia and was associated with acute hemiplegic stroke and an absent radial pulse. The possible mechanism of embolization and the implications for the selection and management of patients undergoing TEE are discussed.

Influence of carotid baroreceptors on different components of the vascular system.

1. Reflex changes in wall tension of the lateral saphenous vein of one hind limb, the splenic veins and capsule, and the resistance vessels of the other hind limb caused by changes in baroreceptor activity were measured in vagotomized dogs under thiopentone-chloralose anaesthesia.2. Three different methods were used to alter pressure in one or both carotid sinuses. (1) Both carotid sinuses were vascularly isolated and filled with fully oxygenated Krebs-Ringer bicarbonate solution (pH 7.4) from a reservoir in which the pressure could be altered at will. (2) One sinus was denervated, and the contralateral sinus was perfused with arterial blood at different flow rates. (3) One sinus was denervated, and the innervated sinus was perfused with arterial blood at constant flow, the pressure being altered by changing the outflow resistance.3. The left saphenous vein was perfused at constant flow with autologous blood; changes in perfusion pressure were used as a measure of changes in veno-motor activity. The right common iliac artery was perfused at constant flow to measure changes in resistance vessel activity. Blood flow through the spleen was temporarily arrested, trapping a fixed volume of blood in the organ. Under these conditions, changes in splenic vein pressure were a measure of changes in smooth-muscle tension in the splenic capsule and veins.4. In order to assess the responses to baroreceptor stimulation in terms of alterations in sympathetic nerve traffic to different components of the peripheral vascular system, ;frequency-response curves' were constructed for spleen, saphenous vein, and limb resistance vessels by electrical stimulation of the splenic nerves and lumbar sympathetic chains.5. The saphenous vein showed no consistent response to changes in baroreceptor activity. Reduction in carotid sinus pressure from 180 to 100 mm Hg caused an increase in venous pressure in the isovolumetric spleen and in the iliac artery perfusion pressure. These results were confirmed by electrical stimulation of the carotid sinus nerve. Whereas the peak responses of the limb resistance vessels corresponded to an increase in lumbar sympathetic nerve traffic of 6-10 c/s, the maximal splenic responses were equivalent to an increase in splenic nerve traffic of 1-4 c/s. These results are consistent with selective autonomic nervous control of different components of the peripheral vascular system.

Percutaneous transluminal balloon dilatation of the mitral valve in pregnancy.

Pregnancy can cause life threatening complications in women with mitral stenosis, and there is a substantial risk of fetal death if valvotomy under cardiopulmonary bypass is required. A patient is described in whom pulmonary oedema developed after delivery of her first child by caesarean section 13 months previously. Subsequent cardiac catheterisation showed severe mitral stenosis (valve area 0.96 cm2, valve gradient 12 mm Hg, pulmonary artery pressure 30/16 mm Hg). Before valvotomy could be performed the patient again became pregnant and presented in pulmonary oedema at twenty two weeks' gestation. Medical treatment was unsuccessful and she underwent percutaneous transluminal balloon dilatation of the mitral valve. This increased the valve area to 1.78 cm2 and reduced the transmitral gradient to 6 mm Hg. The procedure was uncomplicated, and she remained symptom free on no medication. She delivered vaginally at 37 weeks' gestation. Percutaneous transluminal balloon dilatation of the mitral valve is a safe and effective alternative to mitral valvotomy in pregnancy.