Decreased post-myocardial infarction heart rate variability and cardiac denervation assessed by metaiodobenzylguanidine scintigraphy.

Decreased heart rate variability, assessed 2 weeks after uncomplicated acute myocardial infarction, is related to the extent of 1-123-metaiodobenzylguanidine-derived efferent sympathetic cardiac denervation. This postinfarction cardiac denervation could be the substrate of reduced postinfarction heart rate variability.

Detection of microinfarction in patients with unstable angina: study by 111In-antimyosin imaging.

To examine the incidence of a positive indium-111 antimyosin scintigraphy in patients with unstable angina, we prospectively examined 25 patients with unstable angina and 11 patients with stable angina. All patients were injected with 2 mCi of indium-111 on admission and planar scintigraphy was performed 48 h later. Symptoms and signs of ischemia indicating severity of ischemia were monitored during the period between injection and scanning. None of the patients developed a rise in cardiac enzymes suggesting myocardial necrosis. Seven (28%) of the 25 patients with unstable angina had positive antimyosin scanning; no stable patients had positive scanning. All seven patients with unstable angina and positive scanning had signs of severe ischemia (four patients had multiple episodes of > 2/day, three patients had prolonged episodes of > 15 min, three patients had ST depression in > 3 EKG leads) while only one of the eighteen unstable patients with negative scannings had signs of severe ischemia (P < 0.001). In conclusion, (1) a significant number of unstable angina patients present positive antimyosin scanning without an elevation of cardiac enzymes and (2) these patients usually present multiple or severe episodes of ischemia indicating that during these episodes, minor myocardial necrosis, undetected by enzymes, may occur.

Acute effects of external and internal pacing on ejection fraction in patients with severe cardiac failure.

The present study aims at evaluating the acute hemodynamic effects of external and internal (3 and 15 mA) pacing on 30 patients with severe cardiac failure. The global and regional ejection fraction were calculated by repeated radionuclide ventriculography at rest (control) and during increasing pacing rates. Blood pressure was measured at the end of each scintigraphy data acquisition period. The pacing rate was increased by 10 beats/min in every step and varied between +10 to +60 beats/min above the resting heart rate. The ejection fraction during pacing was lower than the resting ejection fraction in every pacing mode (resting ejection fraction = 23.30 +/- 7.67%, external pacing = 19.36 +/- 9.30%, p < 0.05, internal pacing 3 mA = 22.15 +/- 7.00%, p = N.S., internal pacing 15 mA = 19.92 +/- 6.95%, p < 0.05). The resting ejection fraction was higher than the ejection fraction in every pacing rate. In 4 out of 30 patients the ejection fraction was higher in every pacing mode and rate than the resting ejection fraction. The regional ejection fraction of the interventricular septum during internal pacing was lower (p < 0.001) than resting and/or external pacing. In conclusion, pacing in patients with severe cardiac failure reduces the control ejection fraction. This reduction increases as the pacing rate increases. The reduction is greater with internal pacing of 15 mA while the hemodynamic effect in external pacing did not differ significantly from internal pacing. Overall, the resting ejection fraction was higher than the paced ejection fraction, although in some patients pacing improved their resting ejection fraction.

I-123 metaiodobenzylguanidine--thallium-201 mismatch following myocardial infarction.

Experimental data show that myocardial infarction (MI) results in regional depletion of myocardial catecholamines more extensively than necrosis. To investigate the extent of adrenergic denervation post MI in humans, we examined 16 patients, 59 +/- 12 years old, with recent (7-12 days) MI. Resting thallium-201 (201Tl) single photon emission computerized tomography (SPECT) imaging was performed to assess necrosis; metaiodobenzylguanidine I123 (MIBG) SPECT was used to evaluate adrenergic denervation. 201Tl and I123 MIBG defects were evaluated quantitatively using polar maps, and differences in defects were expressed as percent of total polar map. In all patients, I123 MIBG defect was larger than 201Tl defect, and difference ranged from 19 to 61% (39.5 +/- 13.2%). Thrombolysis and age > 60 did not influence the difference. Anterior MI showed larger differences (44 +/- 13 vs. 32 +/- 11%, p < 0.05); patients with ischemic electrocardiographic (ECG) changes in leads without abnormal Q waves had larger differences (45 +/- 9 vs. 33 +/- 14%, p < 0.05). It was concluded that (a) patients with recent MI present denervation larger than 201Tl perfusion defect, and (b) patients with anterior MI and ischemic ECG changes present a larger area of denervation.

Detection of viable tissue in healed infarcted myocardium by dipyridamole thallium-201 reinjection and regional wall motion studies.

Reinjection imaging with thallium-201 (Tl-201) may provide a convenient method of assessing myocardial viability. Twenty patients with a previous Q-wave healed myocardial infarction were examined to evaluate the detection of viable tissue in infarcted segments. All patients underwent to evaluate the detection of viable tissue in infarcted segments. All patients underwent dipyridamole Tl-201 tomographic imaging with reinjection of 1 mCi of Tl-201 after redistribution. Radionuclide ventriculography was performed before and after administration of 5 mg of dinitrate isosorbide sublingually for regional wall motion analysis. Patients presented with 38 fixed defects, 12 of which demonstrated improved Tl-201 uptake on reinjection; 10 of 12 reinjection-reversible segments were hypokinetic or normal after administration of nitrates, whereas 22 of 26 nonreversible segments remained akinetic or dyskinetic (p < 0.001). Of 20 patients, 9 had reinjection-reversible segments; coronary angiography revealed a patent infarct-related artery or collaterals, or both, in 7 of these patients. The infarct-related artery was patent or collaterals were present, or both, in 4 of 11 patients who did not improve with reinjection. It is concluded that reinjection of Tl-201 during dipyridamole Tl-201 scintigraphy may frequently detect viable tissue in infarcted segments in patients with a Q-wave infarction. Segments with reinjection reversibility usually do not remain dyskinetic or akinetic after administration of nitrates and have some residual flow on coronary angiography.

Doxorubicin cardiotoxicity detected by indium 111 myosin-specific imaging.

A patient with primary hepatoma, treated with doxorubicin and presenting with atypical electrocardiographic findings, was investigated with myosin-specific monoclonal antibody radiolabelled with indium-111. Despite a normal ejection fraction, myosin-specific scintigraphy was positive, indicating doxorubicin cardiotoxicity.

Amoxicillin and clavulanic acid combination: clinical and laboratory evaluation in pulmonary infections.

Twenty-four patients with pulmonary infections (7 pneumoniae, 17 exacerbations of chronic bronchitis) were treated with a combination of 250 mg of amoxicillin and 125 mg of clavulanic acid supplemented by 500 mg of amoxicillin every eight hours. All patients showed good clinical, roentgenological, and bacteriological response. Bacteria were cleared from sputum by the third day of treatment in half of the patients and by the end of treatment in all but one of the others. Pathogens eradicated from sputum, with concurrent clinical cure, included gram-negative bacteria producing cephalosporinases shown to be resistant to the combination drug by both disk and minimal inhibitory concentration determinations.