M M Webb-Peploe

RELATION BETWEEN INTERATRIAL SHUNTS AND DECOMPRESSION SICKNESS IN DIVERS

The prevalence of right-to-left interatrial shunts was determined by contrast echocardiography in a blind comparison of 61 divers who had had decompression sickness, divided into four predetermined clinical subgroups, and a control group of 63 who had not. The prevalence of shunt was 15/63 in the controls and did not differ significantly in 24 divers with onset of neurological symptoms more than 30 minutes after surfacing (4/24) or 6 with joint pain only (1/6). In divers who had neurological symptoms within 30 minutes of surfacing the prevalence of shunt was 19/29, significantly higher. Rashes soon after surfacing were related to shunts but late rashes were not.

Coronary artery ectasia--a variant of occlusive coronary arteriosclerosis.

In a study of 1000 consecutive coronary arteriograms, 12 patients (all men) had coronary artery ectasia. Ectasia was found most frequently in the circumflex or right coronary artery. Only 1 patient had ectasia in the left anterior descending coronary artery. In 11 patients, ectasia of one artery was associated with severe stenosis or occlusion of other vessels, typical of arteriosclerosis. Histology from an ectatic segment in one of this group showed changes of severe arteriosclerosis with extensive intimal fibrosis and destruction of the media. One patient had a mixed collagen vascular disease. Measurement of coronary sinus flow in 2 patients with coronary artery ectasia showed flows in the range of patients with non-ectatic coronary artery disease. At cardiac surgery flows down the graft to ectatic arteries were in the same range as in grafts to non-ectatic vessels. Patients with coronary artery ectasia should be anticoagulated.

COLD-INDUCED PULMONARY OEDEMA IN SCUBA DIVERS AND SWIMMERS AND SUBSEQUENT DEVELOPMENT OF HYPERTENSION

The effect of cold and/or a raised partial pressure of oxygen was examined in eleven people with no demonstrable cardiac abnormality but who had pulmonary oedema when scuba diving or surface swimming, and in ten normal divers. These stimuli induced pathological vasoconstriction in the pulmonary oedema group, nine of whom also showed signs of cardiac decompensation when so stimulated. The pulmonary oedema patients have been followed-up for an average of 8 years. Seven have become hypertensive. Except for the onset of lone atrial fibrillation in one normotensive female diver and development of Raynauds phenomenon in a normotensive man, there have been no cardiovascular events and no deaths.

Enzymic analysis of endomyocardial biopsy specimens from patients with cardiomyopathies.

Myocardial biopsies have been obtained from patients with hypertrophic or congestive cardiomyopathies. Marker enzymes for the principal subcellular organelles of the myocardium were estimated using highly sensitive assay procedures. The results were compared with those obtained in tissue from patients with valvular heart disease with good or poor left ventricular function. Left ventricular myocardial tissue from patients with hypertrophic cardiomyopathy showed essentially normal levels of enzymic activities. In congestive cardiomyopathy, right ventricular tissue showed reduced levels of mitochondrial enzymes with increased levels of lactate dehydrogenase. Left ventricular tissue from patients with congestive cardiomyopathy showed reduced levels of mitochondrial and myofibril enzymes but high levels of lactate dehydrogenase. The reduced levels of myofibril Ca++-activated ATP in congestive cardiomyopathy is similar to that found in patients with impaired left ventricular function secondary to valvular disease. It is suggested that defective mitochondrial function is a characteristic feature of congestive cardiomyopathy and that the increased levels of lactate dehydrogenase reflect a compensatory response.

Haemodynamic effects of intravenous amrinone in patients with impaired left ventricular function.

The effects of intravenous amrinone on resting haemodynamic function were investigated in 15 patients with impaired left ventricular function. All patients received 1 X 5 mg/kg and 10 received a further 2 mg/kg. We observed dose related increases in heart rate and cardiac index, and reductions in mean arterial pressure, left ventricular end-diastolic pressure, and systemic vascular resistance. A small reduction in left ventricular end-diastolic volume and a 36% increase in ejection fraction occurred. No significant change in max dp/dt, min dp/dt, (Max dp/dt/P), max (dp/dt/P), KVmax or the ratio of left ventricular end-systolic pressure to left ventricular end-systolic volume was detected. It is concluded that the beneficial effects of intravenous amrinone on the resting haemodynamics in our patients were attributable to vasodilatation, with the drug having no demonstrable positive inotropic effect.

Acute haemodynamic and metabolic effects of dopexamine, a new dopaminergic receptor agonist, in patients with chronic heart failure.

Dopexamine, a new compound with postjunctional dopamine receptor activating and beta adrenoceptor agonist properties, was given to 10 patients with chronic heart failure at diagnostic cardiac catheterisation to investigate its acute haemodynamic and metabolic effects. The drug was administered by intravenous infusion in three incremental doses and produced significant dose related increases in cardiac index, stroke volume index, and heart rate and falls in systemic vascular resistance and left ventricular end diastolic pressure; aortic and pulmonary artery pressures were unchanged. Isovolumic phase (max dP/dt and KVmax) and ejection phase (peak aortic blood velocity, maximum acceleration of blood, and maximum rate of change of power with time during ejection) indices of myocardial contractility were all increased by dopexamine but these changes were hard to interpret in the presence of an increase in heart rate. Myocardial efficiency and ejection fraction were both increased and left ventricular end diastolic and end systolic volumes fell. These largely beneficial changes were achieved without a statistically significant increase in myocardial oxygen consumption or disturbance of myocardial metabolic function. Dopexamine was well tolerated but tremor was reported by two patients at the intermediate dose and mild chest pain by two patients at the high dose.

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.

Thallium-201 myocardial imaging in patients with dilated and ischaemic cardiomyopathy.

Ischaemic cardiomyopathy and dilated cardiomyopathy may be clinically indistinguishable and cardiac catheterisation is often required to differentiate between them. We have described the thallium-201 scintigraphic appearances both on exercise and after redistribution in 13 patients with ischaemic cardiomyopathy and 11 patients with dilated cardiomyopathy and have assessed the usefulness of this non-invasive technique in distinguishing between the two groups. All patients with ischaemic cardiomyopathy and seven of the 11 patients with dilated cardiomyopathy displayed perfusion defects. Reversible defects were equally common in the two

Radiation exposure of patients and coronary arteries in the stent era: A prospective study

Previous studies have investigated the radiation dose to doctors and patients during coronary angiography and angioplasty, but most of them were retrospective, conducted in the prestent era, and results have not been consistent. Effective dose of 57 patients undergoing coronary angiography and/or angioplasty was assessed by using a dose‐area product (DAP) to effective dose conversion factor. Radiation exposure risks to patients were then calculated for each procedure. Thermoluminescent dosimeters, mounted on a specially designed catheter that was advanced to the left or right sinus of Valsalva, were used to measure the dose received by the coronary arteries. Mean effective dose received by patients were 5.0 ± 0.5 mSv for coronary angiography, 6.6 ± 1.0 mSv for angioplasty, 10.2 ± 1.5 mSv for angioplasty followed by stent implantation, 13.6 ± 2.5 mSv for angiography followed by ad hoc angioplasty, and 16.7 ± 2.8 mSv for angiography followed by ad hoc angioplasty and stent implantation. Patient risk of developing cancer after each procedure was 0.025%, 0.033%, 0.051%, 0.068%, and 0.084%, respectively. Corresponding mean coronary irradiation doses were 24 ± 2.5, 31.0 ± 3.6, 43.6 ± 7.2, 55.0 ± 7.5, and 64.7 ± 5.6 mGy, respectively. A linear relationship of the DAP and the dose at the coronary arteries was found: DAP = 1,273 (cm2) × coronary dose (mGy). Radiation exposure to coronary arteries and associated risk to patients are relatively low, even following complicated, multivessel angioplasty with stent implantation. Our method can be used for calculation of radiation risk to patients and radiation dose to coronary arteries by using external dosimeters. Cathet. Cardiovasc. Intervent. 51:259–264, 2000.

Comparison of the effects of amrinone and sodium nitroprusside on haemodynamics, contractility, and myocardial metabolism in patients with cardiac failure due to coronary artery disease and dilated cardiomyopathy.

The effects of intravenous amrinone and sodium nitroprusside on haemodynamic indices, left ventricular contractility, and myocardial metabolism were compared in patients with cardiac failure. All patients received one dose of each drug and some received serial doses. Eight patients had dilated cardiomyopathy and six coronary artery disease, but the responses to the two drugs were independent of the aetiology of cardiac failure. Both drugs lowered left ventricular end diastolic pressure and aortocoronary sinus oxygen difference and increased cardiac index and left ventricular efficiency; these effects were dose related. Although the effects of the drugs on peripheral blood substrate concentrations were different, those on myocardial substrate metabolism were identical. Pressure derived indices of contractility in each group of patients were unaltered by either drug. After amrinone administration increases in cardiac index were related to plasma amrinone concentration, but alterations in contractility were not. In four individual patients increases in contractility were associated with alterations in plasma metabolite concentrations, which suggested that catecholamine release had occurred. For the groups of patients as a whole, however, amrinone had effects which did not differ significantly from those of the pure vasodilator, nitroprusside. There was no evidence that amrinone had a direct positive inotropic effect since no dose related changes in indices of contractile function could be established.