E. Hoffer

Low-level exercise echocardiography detects contractile reserve and predicts reversible dysfunction after acute myocardial infarction: Comparison with low-dose dobutamine echocardiography

OBJECTIVES The aim of this study was to evaluate low-level exercise echocardiography (LLEE) in detecting contractile reserve and predicting functional improvement of akinetic myocardium early after acute myocardial infarction (AMI). BACKGROUND Experimental and clinical studies have shown that low-dose dobutamine enhances contractile function of dyssynergic but viable myocardium in patients with recent AMI. We hypothesized that endogenous catecholamines produced during a LLEE test could serve as a myocardial stressor to elicit contractile reserve. METHODS Fifty-two consecutive patients with first AMI and > or =2 akinetic segments in the infarct-related territory underwent 5 +/- 2 days after AMI low-dose dobutamine echocardiography (LDDE) (5, 10 and 15 microg/kg/min) and LLEE (25 W during 3 min on a supine bicycle, with continuous echocardiographic recording). Both tests were performed on the same day, in random order. Follow-up echocardiography was obtained one month later. Regional wall thickening was semi-quantitatively assessed using a 16-segment, 5-grade scale model. Contractile reserve was defined as improvement in wall thickening of > or =1 grade. RESULTS Mean increase in heart rate during stress tests was 15 +/- 7 beats/min with LLEE and 13 +/- 6 beats/min with LDDE (p = NS). Contractile reserve was detected in 119 (55%) of 217 akinetic segments at LLEE and in 137 (63%) segments at LDDE. At follow-up study, functional improvement was identified in 139 (64%) segments. Sensitivity, specificity and positive and negative predictive values for predicting functional recovery were 81%, 92%, 95% and 73%, respectively, for LLEE, and 91%, 86%, 92% and 84%, respectively, for LDDE. Moreover, there was a good correlation between systolic wall thickening measured in the center of the dyssynergic area during stress tests and at follow-up study: r = 0.77, p < 0.001 with exercise testing and r = 0.73, p < 0.001 with dobutamine testing. CONCLUSIONS Low-level exercise echocardiography provides a promising alternative to LDDE for identifying myocardial viability and predicting reversible dysfunction early after AMI.

Detection and clinical usefulness of a biphasic response during exercise echocardiography early after myocardial infarction

OBJECTIVE The aim of this study was to determine the accuracy of exercise echocardiography (EE) for detecting infarct-related artery (IRA) stenosis and predicting functional recovery early after acute myocardial infarction (AMI). BACKGROUND Dobutamine stress echocardiography is widely used for identifying jeopardized myocardium. The clinical usefulness of a biphasic response detected during EE has never been investigated. METHODS A total of 114 consecutive patients with a first AMI and > or = 2 dyssynergic segments in the infarct-related territory underwent semi-supine continuous EE 6 +/- 2 days after AMI. Quantitative coronary angiography was performed in all patients after EE. A follow-up echocardiogram was obtained one month later. RESULTS Ninety-seven patients had significant (> or = 50%) IRA stenosis, and 26 had multivessel disease. Residual ischemia was identified in 77 patients (biphasic response in 62 and worsening response in 15). The sensitivity and specificity of ischemia during EE for predicting IRA stenosis were 75% and 76%, respectively. The sensitivity of a biphasic response was higher than the sensitivity of a worsening response (61% vs. 14%, p < 0.0001). Wall motion abnormalities induced in other vascular territories were specific (97%) and moderately sensitive (62%) for the detection of multivessel disease. Functional recovery was observed in 75 patients. Two independent variables predicted contractile recovery: contractile reserve during EE (p < 0.0001) and elective angioplasty of the IRA (p = 0.002). A biphasic response, but not sustained improvement, predicted reversible dysfunction (73% vs. 9%, p < 0.0001). CONCLUSIONS A biphasic response can be detected during exercise. Exercise echocardiography is an accurate tool for detecting IRA stenosis and predicting functional improvement early after AMI.

Role of stress echocardiography in heart failure

Most patients presenting with heart failure have severe coronary artery disease. The identification of viable hibernating myocardium is of paramount clinical importance for a correct indication of revascularization. Contractile reserve may be identified when regional asynergy improves during low or moderate doses of dobutamine. Dipyridamole, given at infra-low dose, alone or preferably in association with a low dose of dobutamine, is another possible pharmacologic stress protocol. Dobutamine echocardiography has been found to be more specific than thallium scintigraphy for predicting functional recovery after revascularization. However, the absence of contractile reserve does not exclude the presence of myocardial viability: perfusion reserve may be too low because of a critical coronary artery stenosis, or profound ultrastructural changes of myocardial cells may be present, including significant loss of contractile material. Inotropic reserve can also be assessed by dobutamine stress echocardiography in patients with idiopathic cardiomyopathy. The evolution of hemodynamic variables can be measured during the stress test. Stress echocardiography, especially during exercise, could probably provide important information about heart failure associated with valvular heart disease.

Short-term effect of atorvastatin on ischaemic threshold in hypercholesterolaemic patients with stable ischaemic heart disease

Objective — Hypercholesterolaemia is associated with a loss of endothelium-dependent vasodilation, which may facilitate the occurrence of myocardial ischaemia in patients with coronary artery disease (CAD). The improvement of endothelial dilator function after 4 to 6 weeks of oral lipidlowering therapy has been documented. Whether this early restoration of endothelial function by statins translates into anti-ischaemic effects is unknown.This study was designed to determine the effect of 4 weeks’ treatment with 80 mg atorvastatin daily on exercise-induced ischaemia in patients with stable ischaemic heart disease (IHD) receiving standard anti-anginal drug therapy. Methods and results — A total of 41 patients with documented CAD, exercise-induced ischaemia and LDL-cholesterol > 130 mg/dl underwent exercise ECG, angina score and lipid level assessment at baseline, after 4 weeks of placebo treatment, and after 4 weeks of therapy with atorvastatin 80 mg. Primary endpoint was the change in time to 1 mm ST-segment depression (= ischaemic threshold) between placebo and treatment period. Atorvastatin treatment resulted in a 55% reduction of low-density lipoprotein (LDL) cholesterol (from mean of 162 (SD 32) to 72 (20) mg/dl). For a comparable rate-pressure product, the average time to 1 mm ST-segment depression was 295 (112) s at baseline, 314 (149) s after placebo and 301 (131) s after atorvastatin, indicating that the ischaemic threshold was not significantly modulated after 4 weeks of atorvastatin treatment.There was also no significant change in global angina score or in time to maximal ST-segment depression. Conclusions — High-dose atorvastatin treatment for 4 weeks drastically reduced LDLcholesterol. However, the present study did not demonstrate a significant effect on the ischaemic threshold in patients with stable IHD already under treatment with anti-ischaemic agents.

Stenosis of a mechanical mitral prosthetic valve in a patient with systemic lupus erythematosus.

A young woman with systemic lupus erythematosus (SLE) developed progressive heart failure several years after mitral valve replacement with a Björk-Shiley prosthesis for treating mitral stenosis due to Libman-Sacks endocarditis. She was admitted to the hospital with pulmonary oedema. Transoesophageal echocardiography revealed stenosis of the mitral prosthesis, which was covered by fibrous tissue. Replacement of the prosthesis was done but the patient died from cerebral haemorrhage three days later. Although three cases of prosthetic valve dysfunction in SLE have been documented so far, this is to our knowledge the first report of a SLE recurrence on a tilting disc mechanical valve.