Assessment of the mitral valve splitability score by transthoracic and transesophageal echocardiography.
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Echocardiography↗
Biomedical subjects
T H Marwick
Publications and source records attributed to T H Marwick.
Identification of ischemic and hibernating myocardium: feasibility of post-exercise F-18 deoxyglucose positron emission tomography.
The identification of ischemic and hibernating myocardium facilitates the selection of patients most likely to benefit from revascularization. This study examined the feasibility of metabolic imaging, using post-exercise F-18 deoxyglucose positron emission tomography (FDG-PET) for the diagnosis of both ischemia and hibernation in 27 patients with known coronary anatomy. Normal post-exercise FDG uptake was defined in each patient by reference to normal resting perfusion and normal coronary supply. Abnormal elevation of FDG (ischemia or hibernation) was compared in 13 myocardial segments in each patient, with the results of dipyridamole stress perfusion imaging performed by rubidium-82 positron emission tomography (Rb-PET). Myocardial ischemia was diagnosed by either FDG-PET or Rb-PET in 34 segments subtended by significant local coronary stenoses. Increased FDG uptake was present in 32/34 (94%) and a reversible perfusion defect was identified by Rb-PET in 22/34 (65%, p less than .01). In 3 patients, ischemia was identified by metabolic imaging alone. In 16 patients with previous myocardial infarction, perfusion defects were present at rest in 89 regions, 30 of which (34%) demonstrated increased FDG uptake, consistent with the presence of hibernation. Increased post-exercise FDG uptake appears to be a sensitive indicator of ischemia and myocardial hibernation. This test may be useful in selecting post-infarction patients for revascularization.
Coronary Disease↗
Diagnostic accuracy of the resting electrocardiogram in detection and estimation of left atrial enlargement: an echocardiographic correlation in 551 patients.
The identification of LA enlargement may have important clinical implications. Previous correlations of ECG P wave morphologies associated with LA enlargement and echocardiography have been limited by the use of small numbers of patients and by the employment of M-mode echocardiography without the benefit of two-dimensional guidance. The purpose of this study was to further examine the sensitivity and specificity of various P wave morphologies (P wave greater than or equal to 110 msec, notched P greater than or equal to 40 msec, and PTFV1 greater than or equal to 40 msec.mm) for the diagnosis of LA enlargement and to determine if these waveforms may be predictive of LA size. ECGs and surface echocardiograms obtained within 1 week of each other were evaluated in 551 patients (140 normal and 411 study subjects). The various P wave morphologies were found to be poorly sensitive (30% to 60%) but very specific (90%) for LA enlargement. Combinations of P wave morphologies did not improve sensitivity or specificity. ECG features did give an estimate of the degree of LA enlargement. When PTFV1 is greater than or equal to 40 msec.mm, 95% of patients had LA size greater than or equal to 40 mm; and when this parameter was greater than or equal to 60 msec.mm, 75% had LA size greater than or equal to 60 mm. These criteria for LA enlargement on the ECG are specific and predictive of the degree of LA enlargement measured by echocardiography.
Atrial Function, Left↗
Mechanisms of failure of mitral valve repair: an echocardiographic study.
Surgical valve repair for mitral regurgitation has significant advantages over valve replacement, but little is known about the mechanisms of its failure. This echocardiographic study examined abnormalities leading to failed mitral valve repair in two populations: "immediate failure" of the valve repair in the operating room requiring a second run of cardiopulmonary bypass and "late failure" of valve repair necessitating reoperation on another occasion. Intraoperative echocardiography (IOE) after cardiopulmonary bypass was performed in 309 patients undergoing valve repair for mitral regurgitation over a 3-year period. Twenty-six (8%) of these patients had immediate failure of the repair demonstrated by IOE, requiring further repair or replacement during the same thoracotomy. The causes of immediate failure were left ventricular outflow tract obstruction (10 patients), incomplete correction (10 patients), and suture dehiscence (six patients). Echocardiography was performed on 17 patients requiring reoperation for recurrent mitral regurgitation who had undergone previous primary valve repair. These late failures resulted from progressive degenerative leaflet or chordal disease (n = 9) or suture dehiscence of the annular ring or the leaflet resection site (n = 6). In only two patients early in the series did the problem originate from inadequate initial surgery. IOE is an effective marker for unsuccessful mitral valve repair, and affords an understanding of the mechanism of the persistent dysfunction. Immediate failure of mitral repair may be reduced by greater attention to the mechanism of valve dysfunction and by changes in valvuloplasty technique to avoid outflow tract obstruction. Late failure after mitral repair occurs predominantly due to progression of disease, particularly in patients with severe myxomatous or annular abnormalities that are prone to progress.
Adolescent↗
Prognostic significance of right ventricular ejection fraction following inferior myocardial infarction.
The prognostic significance of right ventricular ejection fraction, measured by radionuclide ventriculography, was assessed in 168 consecutive patients with inferior myocardial infarction. Right ventricular ejection fraction was 0.40 or less in 35 patients. Over a follow-up period of 40 months, there were 15 deaths in the total group of 168 patients, eight (23%) in the 35 with right ventricular ejection fraction of 0.40 or less, and seven (5%) in the remainder of the group. The one year survival of patients with right ventricular impairment (84 +/- 6%) was significantly worse (P less than 0.01) than those with a right ventricular ejection fraction over 0.40 (95 +/- 2%). A multivariate Cox model analysis showed age (P less than 0.001), left ventricular ejection fraction (P less than 0.01), and right ventricular ejection fraction (P less than 0.03) to be independent predictors of survival. Impaired right ventricular function is an adverse prognostic factor in patients with inferior infarction, particularly in those with impaired left ventricular function.
Female↗
Prediction of survival from resuscitation: a prognostic index derived from multivariate logistic model analysis.
Despite advances in resuscitation, the ability to predict survival at cardiac arrests remains unsophisticated. We identified the factors determining outcome of all cardiopulmonary resuscitations performed at our institution over a 4-year period, and used a Cox multivariate regression model to design prognostic indices to assess the probability of successful resuscitation and hospital discharge. Cardiac arrests (710) were studied, and 193 (28%) were successfully resuscitated. The most influential variables, judged by the size and significance of their logistic regression coefficients, were rhythm, resuscitation delay, and age (for successful resuscitation), and rhythm, performance of intubation and defibrillation, defibrillation delay, and age (for survival until discharge). The combination of these in a prognostic index reliably predicted both outcome (area under the receiver operating curve of 0.78), and survival until discharge (area under the curve of 0.80).
Aged↗
Myocardial perfusion imaging with positron emission tomography and single photon emission computed tomography: frequency and causes of disparate results.
The purpose of this study was to compare rubidium-82 PET with thallium-201 SPECT imaging in 150 patients. Both techniques followed a single dipyridamole-handgrip stress, and images were displayed using the same 3-dimensional format and quantitative colour scale. Coronary arteriography was employed to assign the correct diagnosis in situations of disparity. Results of PET and SPECT were at least partially concordant in 110 patients (73%), although 22 had more than one defect. A reversible perfusion defect was identified in 60 patients, but the scans were concordant in only 20 (33%). These disparities were chiefly due to false-negative SPECT imaging (22 patients, 55%), and probable delayed thallium redistribution (13 patients, 33%). No patients had ischaemia correctly identified by SPECT in the presence of normal PET imaging. Persistent defects were identified in 91 patients, some of whom also had reversible defects, and the results were consistent in 54 (59%). Other than the delayed thallium redistribution group, the major categories causing disparities were false-positive (6 patients, 16%), and false negative SPECT (8 patients, 22%), attributable to attenuation and scatter. PET appears able to identify smaller, less ischaemic areas subtended by milder coronary stenoses. The availability of a true resting scan with Rb-PET enhances the discrimination between ischaemia and infarction. Attenuation correction, and the high energy photons of positron annihilation, yield more accurate evaluation of inferior wall defects and greater specificity in the presence of soft tissue attenuation.
Adult↗
Transcranial Doppler ultrasound identifies patients with right-to-left cardiac or pulmonary shunts.
We performed transcranial Doppler ultrasound (TCD) and transesophageal contrast echocardiography simultaneously in four patients. In one patient with a patent foramen ovale and another patient with pulmonary A-V fistulae, we detected micro air bubbles in the right middle cerebral artery three to five cardiac cycles after their appearance in the left atrium following intravenous injection of contrast. In two patients without right-to-left shunts, we did not detect air bubbles in the left atrium or middle cerebral artery following injection of contrast. These results show that TCD can identify patients with right-to-left cardiac or pulmonary shunts.
Adult↗
Exercise two-dimensional echocardiography and Doppler assessment of left ventricular function.
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Coronary Disease↗
Influence of left ventricular mass on the diagnostic accuracy of myocardial perfusion imaging using positron emission tomography with dipyridamole stress.
This study assesses the influence of left ventricular hypertrophy (LVH) on the accuracy of myocardial perfusion imaging using pharmacologic coronary vasodilation. Seventy-five patients without previous infarction, and with known coronary anatomy, were studied by echocardiography and PET. LVH (defined by mass greater than 131 g/m2 in males or greater than 100 g/m2 in females) was identified in 25 patients; this group did not differ significantly from the remainder in terms of clinical or angiographic parameters. Twenty patients with hypertrophy had significant coronary artery stenoses, which were identified correctly by PET in 11 (55%), in contrast to 29 of 34 patients (85%, p = 0.03) with coronary disease but normal LV mass. Normal perfusion images were obtained in three of five patients (60%) with hypertrophy but no coronary disease; in contrast, 14 of 16 patients without either coronary disease or hypertrophy (88%, p = ns) had normal scans. The accuracy of PET was 14/25 (56%) in those with hypertrophy, and 43/50 (86%, p = 0.01) in patients with normal LV mass. In this group, the presence of hypertrophy was associated with reduction in the diagnostic accuracy of PET using dipyridamole stress. These findings may account for the phenomenon of "dipyridamole nonresponsiveness" in some patients.
Adult↗
Dipyridamole thallium imaging may not be a reliable screening test for coronary artery disease in patients undergoing vascular surgery.
Dipyridamole thallium imaging has been proposed for cardiac risk stratification in patients undergoing peripheral vascular surgery. The purpose of this study was to define the benefit of this investigation in routine preoperative evaluation of these patients. The outcome of 86 patients undergoing vascular surgery procedures was examined in light of preoperative clinical assessment and dipyridamole SPECT thallium imaging (DST). Fifty-one patients (59%) were considered at high risk on clinical grounds, and 22 patients (26%) had perfusion defects. Ten patients suffered a perioperative coronary event, including unstable angina, myocardial infarction, or cardiac death. Seven of the patients with such events were among the 51 clinically high-risk subjects (14%). Three perioperative events occurred in the group of 19 patients with positive DST images who underwent surgery (16%), but the DST test failed to identify 7 patients who suffered coronary events. The frequency of abnormal thallium imaging was similar to the prevalence of angiographically significant coronary disease reported previously at this center, but considerably less than the rate of abnormal thallium imaging in past studies of vascular surgery patients. The application of the test to a low to moderate risk population is probably responsible for its lower predictive accuracy for coronary events. DST is not an ideal routine noninvasive technique for risk stratification in patients undergoing vascular surgery.
Aged↗
Acute myocardial infarction associated with intravenous dipyridamole for rubidium-82 PET imaging.
This report describes the occurrence of chest pain and electrocardiographic features of acute myocardial infarction following intravenous dipyridamole-handgrip stress. Myocardial perfusion imaging (Rb-82 PET) demonstrated a stress-induced perfusion defect. Following failure to respond to medical therapy, urgent cardiac catheterization demonstrated total occlusion of the left anterior descending coronary artery. The vessel was revascularized, with limitation of myocardial damage evidenced by failure to develop anterior Q waves and only modest elevation of cardiac enzyme levels. Complications of intravenous dipyridamole stress are rare, this case constituting the first major problem in over 500 such procedures at this institution. However, this experience demonstrates the importance of vigilant observation during the performance of this technique.
Dipyridamole↗
Use of the 82Sr/82Rb generator in clinical PET studies.
The use of the 82Sr/82Rb generator in clinical positron emission tomography (PET) studies of myocardial perfusion has been described. An infusion pump is used to deliver the short-lived 82Rb from the generator to the patient. Various characteristics of the generator and the infusion system are described. The 82Rb yield was 69.8 +/- 13.3% and the 82Sr breakthrough was always less than the limit of 0.02 microCi/mCi 82Rb. The yield of 82Rb increased with the flow rate and the potency of the generator. Patients with coronary artery disease were studied for myocardial perfusion abnormalities by the 82Rb PET technique and images of excellent diagnostic quality were obtained.
Coronary Circulation↗
A new method of scoring coronary angiograms to reflect extent of coronary atherosclerosis and improve correlation with major risk factors.
We developed a new angiographic score of the extent of coronary disease (extent score), which we compared with conventional stenosis and vessel scores that emphasize the severity of stenosis. Scores were determined in 132 patients (29 women, 103 men with a mean age of 55 +/- 10 years) who underwent elective coronary angiography. Risk factors were more closely related to the extent score than to either the stenosis or vessel scores (Total R2 = 0.35 versus 0.28 (p less than 0.001) and 0.25 (p less than 0.001), respectively). The extent score was more closely related to age (r = 0.30, p less than 0.05), than was either stenosis (r = 0.21 ns) or vessel score (r = 0.26, p less than 0.05). Apolipoprotein B was the strongest predictor of both extent and stenosis scores but was more closely related to the extent score (r = 0.36, p less than 0.05), even after correction for age and gender. This new angiographic score that assesses the extent of coronary disease is simple to perform and correlates better with age and lipoprotein risk factors than conventional scores do.
Adrenergic beta-Antagonists↗
Left ventricular hypertrophy sensitizes the myocardium to the development of ischaemia.
To evaluate the effects of left ventricular hypertrophy in the development of myocardial ischaemia as detected by thallium-201 exercise scintigraphy, we studied 150 patients by two-dimensional echocardiography, SPECT thallium-201 scintigraphy, and coronary arteriography. Patients were divided into four groups according to the presence or absence of left ventricular hypertrophy and coronary artery disease. There were 62 patients with coronary artery disease and 28 with left ventricular hypertrophy. Left ventricular mass index ranged from a mean of 91.2 g m-2 in the no LVH no CAD group, to a mean of 150.6 g m-2 in the LVH CAD group. For the whole group, the sensitivity of thallium for the detection of coronary artery disease was 82%, specificity 75%, positive predictive value 70%, and negative predictive value 86%. The proportion of patients with abnormal thallium was highest (100%) in the group with left ventricular hypertrophy and coronary artery disease. The second largest group with abnormal perfusion by thallium imaging comprised patients with coronary artery disease and no left ventricular hypertrophy (78%). Both coronary artery disease and left ventricular mass index were demonstrated to be independent predictors of myocardial ischaemia in a multivariate regression model (P = 0.01). We conclude that left ventricular hypertrophy sensitizes the myocardium for the development of ischaemia.
Adult↗
Ineffectiveness of dipyridamole SPECT thallium imaging as a screening technique for coronary artery disease in patients with end-stage renal failure.
The efficacy of dipyridamole single photon emission computed tomography (SPECT) thallium as a screening test for coronary artery disease (CAD), was studied in 45 patients with end-stage renal failure undergoing evaluation for renal transplantation. Coronary arteriography, dipyridamole SPECT thallium imaging and clinical follow-up were performed in all patients. Nineteen patients (42%) had an obstruction of 50% or more in at least one coronary artery. Fourteen patients had a positive thallium scan, but 7 of these were false-positives (sensitivity 37%, specificity 73%). The sensitivity was considerably lower than that quoted for non-ESRF patients in the literature, and significantly lower than a control group of 19 patients without ESRF having comparable severity and distribution of CAD. Five of the 6 patients who died of cardiac causes over a mean follow-up period of 25 months had normal thallium imaging, but all had significant coronary artery disease at cardiac catheterization. Dipyridamole SPECT thallium imaging has not proved a useful screening test for angiographically significant CAD, and does not predict cardiac prognosis in this population.
Adult↗
A prospective comparison of rubidium-82 PET and thallium-201 SPECT myocardial perfusion imaging utilizing a single dipyridamole stress in the diagnosis of coronary artery disease.
The purpose of the present study is to prospectively compare myocardial perfusion imaging with rubidium-82 (82Rb) by positron emission tomography (PET) with thallium-201 (201Tl) imaging by single-photon emission tomography (SPECT) by recording both studies with a single dipyridamole handgrip stress, and reading both sets of images with the same display technique. In a series of 202 patients with previous coronary arteriography, the sensitivity, specificity, and accuracy of 82Rb PET were 93%, 78%, and 90% and for 201Tl SPECT 76%, 80%, and 77%, respectively. When 70 patients with previous therapeutic interventions were excluded, the remaining 132 patients showed a sensitivity, specificity, and accuracy of 95%, 82% and 92% for 82Rb PET and 79%, 76%, and 78% for 201Tl SPECT. The improved contrast resolution of PET resulted in markedly superior images and a more confident identification of defects.
Coronary Circulation↗
Adverse effect of early high-dose adrenaline on outcome of ventricular fibrillation.
Resuscitation for cardiac arrest was monitored over 4 years to examine the effect on survival of a change in the ventricular fibrillation (VF) protocol to include the routine early use of "high-dose" intravenous or transbronchial adrenaline. A significant reduction in the immediate survival of patients with VF was seen when the protocol was changed (22% after the change, 43% before). Prior predictors of poor response were similar in each group, except for the number of witnessed arrests, delay until cardiopulmonary resuscitation, and occurrence of endotracheal intubation, but multiple logistic regression showed the use of adrenaline to be an independent predictor of outcome. Early high-dose adrenaline was associated with a reduction in immediate survival in patients with persistent VF.
Aged↗