Supradiaphragmatic middle aorta syndrome--MR and angiographic imaging

We describe the case of an asymptomatic 24-year-old man with hypertension who was investigated for aortic coarctation but found on MR scanning to have narrowing of the distal thoracic aorta. Stenosis of the thoracolumbar aorta--the Middle Aorta Syndrome--is rare and is usually found below the diaphragm. The MRI and angiographic findings are presented.

Nonvalvular myocardial involvement in metastatic carcinoid disease

A patient with the unusual post mortem finding of myocardial metastatic carcinoid tumour without classical valvular or endocardial carcinoid disease is described. This rare occurrence may represent an aggressive type of carcinoid tumour, with metastatic disease occurring before the development of classical fibrous valvular and endocardial pathology.

Samuel Taylor Chadwick: 1809-73

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A comparison of once and twice daily atenolol for angina pectoris

We have studied the effects of four doses of atenolol in 11 patients with stable angina pectoris using a symptom-limited exercise test and angina diaries. The doses 100 mg twice daily and 50 mg, 100 mg and 200 mg once daily were given double-blind and randomised within patients following run-in on placebo. Measurements were made 12 hours after the last twice daily dose and 24 hours after the last once daily dose. Exercise tolerance was improved by 40-74% and exercise duration before the onset of angina by 61-94% (P less than 0.01). Maximal heart rate was reduced further by a total daily dose of 200 mg than by lower doses, but no extra benefit was derived by giving the drug twice daily. The largest increase in exercise tolerance was obtained during treatment with 50 mg once daily. Atenolol was shown to be an effective anti-anginal agent when given once daily, and there were no major differences between the doses studied.

Effects of propranolol on myocardial oxygen consumption, substrate extraction, and haemodynamics in hypertrophic obstructive cardiomyopathy

Myocardial substrate extraction, coronary sinus flow, cardiac output, and left ventricular pressure were measured at increasing pacing rates before and after propranolol (0.2 mg/kg) in 13 patients with hypertrophic obstructive cardiomyopathy (HOCM) during diagnostic cardiac catheterisation. At the lowest pacing rate myocardial oxygen consumption varied considerably between patients and very high values were found in several individuals (range 10.1 to 57.5 ml/min). These large differences between patients were not explicable by differences in cardiac work; consequently, cardiac efficiency, estimated from the oxygen cost of external work, varied between patients and was lower than normal in all but two. The pattern of substrate extraction at the lowest pacing rate was similar to results reported for the normal heart, and measured oxygen consumption could be accounted for by complete oxidation of the substrates extracted; thus there was no evidence of a gross abnormality of oxidative metabolism, suggesting that low efficiency lay in the utilisation rather than in the production of energy. Each of the four patients with the highest myocardial oxygen consumption and lowest values of efficiency sustained progressive reductions in lactate and pyruvate extraction as heart rate increased, and at the highest pacing rate had low (< 3%) or negative lactate extraction ratios. In three of these four, coronary sinus flow did not increase progressively with each increment in heart rate. One patient with low oxygen consumption and normal efficiency also failed to increase coronary flow with the final increment in heart rate, and produced lactate at the highest pacing rate. Thus the five patients in whom pacing provoked biochemical evidence of ischaemia all had excessive myocardial oxygen demand and/or limited capacity to increase coronary flow. Propranolol did not change lactate extraction significantly at any pacing rate in either the ischaemic or non-ischaemic groups. In only one patient was ischaemia at the highest pacing rate abolished after propranolol, and this was associated with a 30 per cent reduction in oxygen consumption. These results do not demonstrate a direct effect of propranolol upon myocardial metabolism in patients with HOCM, but emphasise the potential value of beta-blockade in protecting these patients from excessive increases in heart rate.

Haemodynamic and metabolic effects of atenolol in patients with angina pectoris

Myocardial substrate extraction, coronary sinus flow, left ventricular pressure, and cardiac output were measured in 11 patients with angina pectoris at three pacing rates before and after atenolol (0.2 mg/kg). Left ventricular pressures, and the product of systolic pressure time index and heart rate did not change, but max dP/dt and KV max fell after atenolol. Only at the lowest pacing rate did the drug reduce cardiac output. Coronary sinus blood flow and myocardial oxygen uptake did not change after atenolol. At the highest pacing rate before atenolol four patients developed angina, accompanied by a rise in end-diastolic pressure. After atenolol angina was abolished in three, but the end-diastolic pressure still rose at the highest pacing rate. Myocardial lactate extraction ratio fell as heart rate increased, and was lower in the patients who developed angina. After atenolol, lactate extraction ratio increased significantly at the highest and lowest pacing rates. Myocardial pyruvate extraction rose after the drug. Arterial concentrations of hydroxybutyrate and acetoacetate fell after atenolol, but the decrease in their extraction was not significant. Myocardial extraction of free fatty acids was related to arterial concentration, which fell after atenolol. The changes in lactate and pyruvate extraction after atenolol were related inversely to changes in arterial free fatty acid concentration suggesting that the improvement in myocardial metabolism could have been secondary to reduced peripheral lipolysis. The increase in lactate extraction was associated with relief of angina, but did not abolish the rise in end-diastolic pressure induced by pacing.

Haemodynamic effects of disopyramide in patients after open-heart surgery

Disopyramide phosphate was administered intravenously in a dose of 1.2 mg/kg body weight over one minute to nine patients after open-heart surgery and coronary artery bypass grafting. The haemodynamic changes were studied during and for 30 minutes after drug administration. Heart rate was unchanged throughout the study. During infusion the only significant changes were an increase in systemic blood pressure and systolic impedance signifying a direct increase in peripheral arterial resistance. Systemic blood pressure remained significantly higher for 10 minutes and systolic impedance for 30 minutes. Immediately after infusion max. dPower/dT, a measure of ventricular contractility, was significantly depressed for 15 minutes. Both cardiac output and aortic flow were significantly depressed for 30 minutes. DPTI/TTI, an estimate of subendocardial supply/demand ratio, showed an insignificant increase throughout the study. This study shows that intravenous disopyramide starts acting within 45 seconds of the start of infusion, directly increases peripheral arterial resistance, has a breif negative inotropic action, and does not reduce subendocardial blood flow.

Atrioventricular dissociation

Examination of the scalar ECG usually allows accurate identification of the various types of AV block. Meticulous attention to waveform identification and careful measurement are the essentials in this as in other fields of electrocardiography. In difficult cases, or where the defect is intermittent, additional recording techniques or special manoeuvres may be necessary. Modern techniques including multichannel ambulatory monitoring, stress testing, physiological and pharmacological manoeuvres, and recording of special surface and intracardiac ECGs are occasionally necessary.