For the purpose of risk stratification 80 consecutive patients (mean age 58 +/- 7) with a chest pain syndrome after documented myocardial infarction underwent tomographic vasodilation-redistribution ...thallium-201 perfusion imaging, using 0.56 mg/kg intravenous dipyridamole. Tomograms were analyzed for size and location of reversible and fixed perfusion defects and correlated to angiographic characteristics, left ventricular ejection fraction and wall motion, collateral status, and 1-year prognosis as measured by cardiac events within 14 +/- 3 months. No serious side effects were noted with the diagnostic use of intravenous dipyridamole. According to the perfusion pattern three subgroups of post-infarction patients were identified: 1) by ischemia at a distance with redistribution in non-infarct related territories (n = 48), 2) by peri-infarctional ischemia with redistribution in the territory of the "infarct artery" (n = 9), and 3) by exclusively fixed defects without redistribution (n = 23). Ischemia at a distance was associated with a larger reversible defect than peri-infarctional ischemia (p less than 0.05) and the pattern without redistribution (p less than 0.005); the fixed defect size, however, was similar in all three subgroups. In addition, the severity of coronary artery disease (Gensini score and number of diseased vessels) and the degree of collateralization was higher in presence of a redistribution pattern (p less than 0.05), although no significant differences in global and regional function were noted as a function of thallium-201 redistribution.
Twenty-nine consecutive patients with symptomatic hypertrophic cardiomyopathy and a mean age of 44.8 +/- 12.2 years (range 21 to 63 years) underwent complex invasive and noninvasive testing in an ...attempt to identify a risk profile for syncope. Clinical, morphologic and electrophysiologic as well as functional parameters at rest and at symptom-limited pacing rate were analyzed for significant association with syncope. Exact stepwise logistic regression analysis identified three variables as significant independent predictors of syncope in hypertrophic cardiomyopathy: 1) age less than 30 years (beta = 4.803; p = 0.0007); 2) left ventricular end-diastolic volume index less than 60 ml/m2 (beta = 3.302; p = 0.006) and 3) non-sustained ventricular tachycardia on 72 h ambulatory ECG monitoring (beta = 2.5909; p = 0.03). The combined occurrence of all three variables had a 100% sensitivity and specificity to identify eight patients with syncopal events. Thus, the risk for syncope in hypertrophic cardiomyopathy is high in young patients with the combination of low left ventricular filling volume and episodes of non-sustained ventricular tachycardia. This finding might also explain the mechanism of syncope in hypertrophic cardiomyopathy as low-input-low-output failure induced by a sudden increase in heart rate in presence of a low filling volume.
The purpose of this study was to assess the reliability of conventional transthoracic and transoesophageal two-dimensional echocardiography combined with color-coded Doppler flow imaging (TEE) and ...ECG-triggered magnetic resonance imaging (MRI) for the diagnosis of thoracic aortic dissection and associated epiphenomena. A total of 53 patients with clinically suspected aortic dissection were subjected to a transthoracic and transoesophageal ultrasound examination and magnetic resonance imaging; the results of each imaging modality were compared and validated against the morphological standards of contrast angiography (n = 53) and/or intraoperative findings (n = 27) or autopsy (n = 7). In this series no deleterious events were encountered with either non-invasive imaging method. In contrast to conventional echocardiography the sensitivities of both MRI and TEE were 100% for detecting a dissection of the thoracic aorta, irrespective of its location. However, the specificity of TEE was lower than the specificity of MRI for a dissection (TEE 68.2% versus MRI 100%; p less than 0.005), which resulted from false positive TEE findings mainly confined to the ascending segment of the aorta (specificity of TEE 78.8% versus 100% by MRI; p less than 0.01). In addition, MRI proved to be more sensitive than TEE in detecting the formation of thrombus in the false lumen of both the aortic arch (p less than 0.01) and the descending segment of the aorta (p less than 0.05). There were no discrepancies between the two imaging techniques in detecting the site of entry to a dissection, aortic regurgitation or pericardial effusion. Both MRI and TEE are atraumatic, safe, and highly sensitive methods to identify and classify acute and subacute dissections of the entire thoracic aorta. However, TEE is associated with lower specificity for lesions in the ascending aorta. These results may still favor TEE after a precursory screening transthoracic echogram in suspected aortic dissection, but will establish MRI as an excellent method to avoid false positive findings. Anatomical mapping by MRI may emerge as a promising comprehensive approach and, eventually, as a morphological standard to guide surgical interventions.
Coronary arteriolar vasodilatation may provoke the redistribution of flow to collateral-dependent jeopardized myocardium. To assess the physiologic significance of collateral channels, 80 consecutive ...postinfarction patients (aged: 58 +/- 8 years) underwent vasodilatation/redistribution thallium-201 tomographic (SPECT) imaging using 0.56 mg dipyridamole/kg body weight. Circumferential profile analysis of redistribution and slow washout in representative left ventricular tomograms provided quantitative evaluation of transient and persistent defects and a separation between a periinfarctional and distant inducible hypoperfusion. Tomographic perfusion data were correlated to subsequent cineangiographic analysis of wall motion and to the extent of collateral circulation between two distinct anatomic perfusion areas, one of which involved the infarct zone. Patients were grouped according to the presence (59%) or absence (41%) of angiographically visible collateral channels to the jeopardized myocardium. In the presence of collaterals, distant reversible defects were larger than in the absence of collaterals (p less than 0.05); the extent of combined periinfarctional and distant redistribution was also larger in collateralized patients (p less than 0.025), whereas the size of the persistent perfusion defect was similar in both groups. In a prospective analysis, the tomographic perfusion pattern of combined periinfarctional and distant ischemia revealed a sensitivity of 85% and a specificity of 78% for the detection of significant collateral circulation in this group of patients. Thus, using the limited collateral flow reserve as a diagnostic tool, vasodilatation/redistribution thallium-201 tomography has some potential for identifying and quantifying collateral-dependent myocardium and may guide diagnostic and therapeutic decision-making.
In 41 patients with a history of an acute myocardial infarction, the location of myocardial ischemia was studied by 201Tl emission computed tomography immediately and 3 h after intravenous ...dipyridamole. Distant ischemia was distinguished from peri-infarctional ischemia by the presence of transient thallium defects in, or slow thallium washout from myocardium not supplied by the infarct-related coronary artery. Ischemia at a distance occurred in 13 patients and was always accompanied by peri-infarctional ischemia. Peri-infarctional ischemia without distant ischemia was observed in 15 patients. The occurrence of distant ischemia was found to be dependent on the severity of stenosis in non-infarct coronary vessels. 12 (86%) of 14 patients with non-infarct stenosis of 75% or greater had distant ischemia, but only 1 (4%) of 27 patients with a stenosis of less than 75% in another vessel. In the presence of distant ischemia, peri-infarctional ischemia was in 11 patients (85%) associated with collaterals supplying the infarct zone, whereas in 13 (87%) of the patients with peri-infarctional ischemia only, incomplete obstruction of the infarct-vessel was observed. It is concluded that, by the distinction between peri-infarctional and distant ischemia, the presence of a significant stenosis in non-infarct vessels can be non-invasively predicted from tomographic thallium scintigraphy with dipyridamole.
A case is reported in which the formation of a right atrial mass was detected by two-dimensional echocardiography 3 weeks after successful transvenous electrical ablation of the atrioventricular ...junction had been performed. The mass was attached to the atrial septum at the site where the electrode catheter used for the ablation had been located and it exhibited no mobility. It was interpreted as a right atrial thrombus induced by the ablation procedure. Although no pulmonary embolic events have been observed during a 7-month follow-up period, right atrial thrombus formation must be considered as a potentially dangerous complication of transvenous catheter ablation to control supraventricular arrhythmias.
