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PubMed2004

Short- and long-term recovery of left ventricular function predicted at the time of primary percutaneous coronary intervention in anterior myocardial infarction.

OBJECTIVES: The aim of this study was to determine predictors of left ventricular (LV) function recovery at the time of primary percutaneous coronary intervention (PCI). BACKGROUND: Angiographic, intracoronary Doppler flow, and electrocardiographic variables have been reported to be predictors of recovery of LV function after acute myocardial infarction (MI). We directly compared the predictive value of Thrombolysis In Myocardial Infarction (TIMI) flow grade, corrected TIMI frame count (cTfc), myocardial blush grade, coronary Doppler flow velocity analysis, and resolution of ST-segment elevation for recovery of LV function in patients undergoing primary PCI for acute MI. METHODS: We prospectively studied 73 patients who underwent PCI for an acute anterior MI. Recovery of global and regional LV function was measured using an echocardiographic 16-segment wall motion index (WMI) before PCI, at 24 h, at one week, and at six months. Directly after successful PCI, coronary flow velocity reserve (CFR), cTfc, TIMI flow grade, and myocardial blush grade were assessed. RESULTS: Mean global and regional WMI improved gradually over time from 1.86 +/- 0.23 before PCI to 1.54 +/- 0.34 at six-month follow-up (p < 0.0001) and from 2.39 +/- 0.30 before PCI to 1.87 +/- 0.48 at six-month follow-up (p < 0.0001), respectively. Multivariate analysis revealed CFR as the only independent predictor for global and regional recovery of LV function at six months. CONCLUSIONS: Doppler-derived CFR is a better prognostic marker for LV function recovery after anterior MI than other currently used parameters of myocardial reperfusion.

Angioplasty, Balloon, Coronary↗

PubMed1999

Recovery rates of regional sympathetic reinnervation and myocardial blood flow after acute myocardial infarction.

BACKGROUND: The implication of an arrhythmogenic role for infarction-induced disruption of regional myocardial sympathetic nerve activity has led to a search for noninvasive methods to study regional sympathetic nerve activity in patients after infarction. METHODS AND RESULTS: By using positron emission tomography, we measured the time course of myocardial hypoperfusion with [13N]-ammonia retention and sympathetic innervation with [18F]-6-fluorodopamine within the infarct zone in 10 patients at 2 weeks, 3 months, and 6 months after a first-onset Q-wave myocardial infarction. The time course for reestablishment of global cardiac autonomic function was also determined by measuring the power spectrum of heart rate variability with an autoregressive technique. The average infarct defect size as determined by the fractional uptake of [13N]-ammonia was 17.22% +/- 5.95% of the left ventricular myocardium. The fractional uptake of [18F]-fluorodopamine in the infarct zone was similar, at 15.83% +/- 4.45% (not significant). There was a significant increase (14% to 15%; P <.05) in myocardial blood flow and [18F]-fluorodopamine uptake to the infarct zone between 2 weeks and 3 months, with no further change between 3 months and 6 months. However, the average rate of loss (t1/ 2 hour) of [18F]- fluorodopamine continued to decrease between 2 weeks and 6 months. This paralleled a continuing fall in the low-frequency to high-frequency autospectral power ratio throughout the 6 months after infarction. CONCLUSIONS: This study demonstrates a modest increase in myocardial blood flow and evidence for sympathetic reinnervation to the infarct zone between 2 weeks and 3 months after acute myocardial infarction. Despite a flow-dependent effect on the uptake of [18F]-fluorodopamine by 3 months, there is a suggestion that restoration of sympathetic activity within the infarct zone continues between 3 months and 6 months after acute myocardial infarction.

Adult↗

PubMed2004

Contraction wave in axial direction in free wall of guinea pig left ventricle.

Mechanical activation of the normal left ventricle (LV) is not simultaneous; however, the potential consequences of the ejection function of the ventricle are not entirely known. We studied contraction of the LV free wall to determine whether it reveals a contraction wave in the axial direction during ejection. Seven guinea pig hearts in situ were studied via thoracotomy. In each heart, the ventricular and aortic pressures were measured by two microtipped manometers (2-Fr, Millar). Contraction of the LV free wall was assessed with a video system (Dalsa D6-0256 camera and EPIX PIXCI D32 frame grabber; acquisition rate, 500 frames/s), and 15-18 epicardial markers were used to divide the region into 20-25 triangular areas. The area sizes were studied during contraction to locate the position of the contraction wave. For each triangular area, two variables were determined as follows: the time (t(c)) from the end of diastole until the size of the area reached 80% of maximum size reduction (normalized with the duration of systole) and the normalized latitude (L(ax)) of the area (determined at the end of diastole). A relationship between these two variables was determined by regression analysis. We found that the t(c) at which the contraction wave reached a triangular area was in positive correlation with the L(ax) value for that triangular area with a slope of 0.25 +/- 0.09 and a linear correlation coefficient of 0.41 +/- 0.08. Thus contraction in the guinea pig LV free wall occurs progressively from apex to base with successive areas reaching 80% contraction.

Animals↗

PubMed2001

Varied tropism of HIV-1 isolates derived from different regions of adult brain cortex discriminate between patients with and without AIDS dementia complex (ADC): evidence for neurotropic HIV variants.

A number of infected individuals develop neuropathological disorders, such as AIDS dementia complex (ADC), as a consequence of HIV/AIDS. The biological features governing HIV entry and tropism in different brain cell types remain unclear, as do the genetics of the virus regulating these events and the neuropathogenic processes within the brain tissues. HIV-1 was isolated from the right and left parietal, occipital, and frontal lobes of the brain cortex of three HIV-1-infected patients: two with ADC and one without. The viral strains were studied from the innate tissues and various primary cell cultures. The kinetics and tropism of viral strains from different brain regions showed clear differences on various primary cell types (monocytes, monocyte-derived macrophages, and T cells), which could discriminate between biological behavior of HIV-1 strains from patients with and without ADC. The variable effect of different donor cells on tropism was also clearly evident. The majority (with a few exceptions) of isolates from different brain regions of all three patients used CCR5 as coreceptor for entry. The consistent CCR5 use, macrophage tropism, and non-syncytium-inducing phenotype were the main characteristics of the brain-derived HIV-1 strains from all three patients. Importantly, viral strains derived directly from innate brain tissue of the patient without ADC showed some differences from the cultured variants of the same patient, whereas those from brain tissue of the patients with ADC were more similar to the culture-adapted strains. This suggests that the emergence of primary cell type-adapted isolates during ADC may play a crucial role in the development and progression of the neuropathology associated with ADC. The different genotypes residing in different areas of brain combined with their differential tropism and coreceptor use suggest that neurotropic variants exist that may be governing the neurological manifestation of HIV disease in infected patients.

AIDS Dementia Complex↗

PubMed1981

Central connections of the posterior lateral line lobe in mormyrid fish.

Primary electroreceptor afferents terminate in the posterior lateral line lobe (PLLL) in electroreceptive teleosts. This paper examines the central connections of PLLL in fish of the family Mormyridae using horseradish peroxidase and tritiated amino acid tracing techniques. Some connections of the closely related lobus caudalis of the cerebellum are also examined. There are three zones on each side of the mormyrid PLLL cortex. Two receive input from mormyromast receptors, and one from ampullary receptors. An intrazonal projection system, intrinsic to PLLL, connects neighboring points within each zone. It also joins corresponding zones on the two sides of the body via commissural fibers. An interzonal system connects the two mormyromast zones on the same side of the midline. Central structures which project to PLLL include lobus caudalis, nucleus paratrigeminalis lateralis, and nucleus praeeminentialis. Nucleus praeeminentialis projects bilaterally and somatotopically to the lower molecular layer of PLLL. PLLL cortex projects bilaterally and somatotopically to two major mesencephalic sites: n. praeeminentialis, and n. lateralis. Somatotopically corresponding points in each zone of PLLL cortex project to the same small region of n. lateralis. Nucleus lateralis has a large and somatotopically organized projection to n. praeeminentialis. The afferent and efferent connections of lobus caudalis are similar to those of PLLL, indicating its close association with the electrosensory system. The anatomical results show that there is ample opportunity for electrosensory information arising on left and right sides of the body to interact centrally. One can suggest that comparison of afferent input from the two sides would reduce the non-significant variability which affects both of them equally. The results also show the presence of several somatotopically organized feedback lops which return the results of higher order processing of electrosensory information to earlier stages.

Afferent Pathways↗

PubMed1981

Ischemic ventricular fibrillation: the importance of being spontaneous.

Although the energy level required to defibrillate normal myocardium is low and constant, as determined from studies of induced ventricular fibrillation, little is known of the specific energy requirements in regionally ischemic hearts for spontaneous or induced ventricular fibrillation. In this study the lowest energy threshold for defibrillation was determined in 10 open chest dogs with reversible 10 minute coronary occlusions at various sites for each of 44 events of ventricular fibrillation, using apical and superior vena caval electrodes with a generator providing variable output of 1 to 30 watt seconds. The ischemic mass, quantitated from postmortem angiographic and planimetric data, was 52 +/- 9 percent (mean +/- standard deviation) of the left ventricle in dogs with induced ventricular fibrillation (Group I), 52 +/- 12 percent in dogs with spontaneous ventricular fibrillation after occlusion (Group II) and 54 +/- 9 percent in dogs with spontaneous ventricular fibrillation after reperfusion (Group III). Defibrillation thresholds in watt seconds were 9 +/- 7 in Group I (n = 12), 19 +/- 10 in Group II (n = 13) and 18 +/- 10 in Group II (n = 19). (Group I versus Groups II and III, probability [p] less than 0.025). In nonischemic hearts, the defibrillation threshold was 3 +/- 2 (n = 32) (p less than 0.001 compared with values in Group I, II or III). Thus, despite similar masses of ischemia, twice as much energy was required for defibrillation of spontaneous ventricular fibrillation (whether after occlusion or reperfusion) as for induced ventricular fibrillation, suggesting that these conditions are caused by different metabolic or pathologic derangements. Such differences should be considered in assessing interventions such as drug therapy designed to inhibit the repetitive ventricular response and in design of implantable defibrillators.

Animals↗

PubMed1983

Incremental value of clinical assessment, supine exercise electrocardiography, and biplane exercise radionuclide ventriculography in the prediction of coronary artery disease in men with chest pain.

The incremental value of clinical assessment, exercise electrocardiography (ECG) and biplane radionuclide ventriculography (RVG) in the prediction of coronary artery disease (CAD) was assessed in 105 men without myocardial infarction who were undergoing coronary angiography for investigation of chest pain. Independent clinical assessment of chest pain was made prospectively by 2 physicians. Graded supine bicycle exercise testing was symptom-limited. Right anterior oblique ECG-gated first-pass RVG and left anterior oblique ECG-gated equilibrium RVG were performed at rest and exercise. Regional wall motion abnormalities were defined by agreement of 2 of 3 blinded observers. A combined strongly positive exercise ECG response was defined as greater than or equal to 2 mm ST depression or 1.0 to 1.9 mm ST depression with exercise-induced chest pain. A multivariate logistic regression model for the preexercise prediction of CAD was derived from the clinical data and selected 2 variables: chest pain class and cholesterol level. A second model assessed the incremental value of the exercise test in prediction of CAD and found 2 exercise variables that improved prediction: RVG wall motion abnormalities, and a combined strongly positive ECG response. Applying the derived predictive models, 37 of the 58 patients (64%) with preexercise probabilities of 10 to 90% crossed either below the 10% probability threshold or above the 90% threshold and 28 (48%) also moved across the 5 and 95% thresholds. Supine exercise testing with ECG and biplane RVG together, but neither test alone, effectively adds to clinical prediction of CAD. It is most useful in men with atypical chest pain and when the ECG and RVG results are concordant.

Adult↗

PubMed1995

Arterial baroreceptors are not essential for low frequency oscillation of arterial pressure.

Cardiovascular parameters exhibit spontaneous oscillations at the respiratory frequency, and in the low frequency range (LF < 0.20 Hz). Although LF is attributed to the sympathetic control, the mechanism responsible for the oscillation, whether instability of the baroreflex loop, or activity of a central nervous system pattern generator, is controversial. To answer this question, time series of arterial blood pressure, heart period and left external iliac blood flow from chloralose-anaesthetised dogs were examined by standard statistics as well as by autoregressive spectral and cross-spectral analysis. The circulation to the left hind-limb was isolated and connected to a constant-pressure perfusing system, to obtain mechanical uncoupling from the central circulation. Three steady-state conditions were studied. A device inserted into the common carotid arteries allowed the carotid sinus region to be in continuity with the animal's arterial system (CONTROL) or perfused at constant pressure by an external source (CAROTID BUFFER); bilateral cervical vagotomy was also performed (VAGI CUT). Intra-individual (beat-to-beat) variability of each parameter was evaluated by standard deviation (SD) of time series in the three conditions. The average SD of heart period was reduced in CAROTID BUFFER and in VAGI CUT; the SDs of arterial pressure and iliac flow were not changed by these interventions. Autospectra of iliac flow time series in CONTROL showed a prominent peak at 0.05 +/- 0.04 Hz (mean +/- SD of all experiments), accounting for 90 +/- 11% of the total variance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

Coronary vasodilator reserve impairment distal to systolic coronary artery compression in dogs.

To investigate the mechanism by which muscular coronary overbridging can cause myocardial ischaemia, we studied the effect of systolic compression (SC) of the proximal left circumflex coronary artery in ten anaesthetised dogs, with both intact autoregulation and maximally dilated coronary arteries. Systolic compression was produced by a mechanical device adjusted to interrupt circumflex coronary flow only during the aortic ejection period and we measured left ventricular, aortic and distal circumflex coronary pressures, phasic coronary blood flow, regional myocardial blood flow (RMBF), myocardial oxygen consumption (MVO2), and myocardial lactate extraction (MLE). During both autoregulation and maximal coronary vasodilatation, there was a diastolic time lag after SC to restart phasic circumflex coronary blood flow (34 +/- 3 vs 31 +/- 3 ms) and to increase distal circumflex coronary pressure (69 +/- 4 vs 79 +/- 6 ms). With autoregulation, SC reduced the diastolic circumflex coronary: systolic left ventricular pressure time ratio (DPTIc:SPTI) and there were no changes in the other measured variables. During maximal coronary vasodilatation and SC, the coronary vasodilator reserve, the DPTIc:SPTI ratio and the inner:outer myocardial blood flow distribution were decreased in the territory of the left circumflex coronary artery; a linear relationship was observed between the DPTIc:SPTI and the inner:outer myocardial blood flow ratio. Systolic compression during vasodilatation also produced a reduction in myocardial oxygen consumption of the whole heart and a production of lactate in the coronary sinus. These results suggest that myocardial ischaemia with a myocardial bridge is due to the combined effects of a diastolic time lag to repressurise the coronary vascular bed, of tachycardia and of coronary vasodilatation.

Animals↗

PubMed1982

EEG findings in senile dementia and normal aging.

EEG findings in 62 patients with senile dementia of alzheimer type (SDA), 22 patients with multi-infarct dementia (MID) and 90 controls of same age and sex were studied. The SDA patients differed significantly from the controls in EEG normality, over-all disturbance, dominant occipital, rhythm, accentuation of theta and delta, fluctuations in alertness, paroxysmal activity and H-reaction. Even the least severely affected SDA patients differed significantly from the controls in all EEG variables except paroxysmal activity. With increasing degree intellectual impairment in the SDA group the dominant occipital rhythm became slower. The MID group differed from the controls in all EEG parameters including asymmetric findings. The EEG findings of the SDA patients differed significantly from those of the MID patients only in asymmetric findings which were more common in the MID patients. 29% of the normal elderly people had EEG alterations, Abnormalities were mild. Asymmetric findings, mainly theta activity in left temporal region were common. H-reaction (occipital driving response greater than or equal to 18 c/s) was well preserved in the controls. EEG is valuable in differentiation of dementia patients from normal elderly people, but differentiation between MID and SDA is not reliable by using EEG, only.

Aged↗

PubMed2005

Bi-hemispheric engagement in the retrieval of autobiographical episodes.

Functional magnetic resonance imaging (fMRI) was used to study the neural correlates of neutral, stressful, negative and positive autobiographical memories. The brain activity produced by these different kinds of episodic memory did not differ significantly, but a common pattern of activation for different kinds of autobiographical memory was revealed that included (1) largely bilateral portions of the medial and superior temporal lobes, hippocampus and parahippocampus, (2) portions of the ventral, medial, superior and dorsolateral prefrontal cortex, (3) the anterior and posterior cingulate, including the retrosplenial, cortex, (4) the parietal cortex, and (5) portions of the cerebellum. The brain regions that were mainly activated constituted an interactive network of temporal and prefrontal areas associated with structures of the extended limbic system. The main bilateral activations with left-sided preponderance probably reflected reactivation of complex semantic and episodic self-related information representations that included previously experienced contexts. In conclusion, the earlier view of a strict left versus right prefrontal laterality in the retrieval of semantic as opposed to episodic autobiographical memory, may have to be modified by considering contextual variables such as task demands and subject variables. Consequently, autobiographical memory integration should be viewed as based on distributed bi-hemispheric neural networks supporting multi-modal, emotionally coloured components of personal episodes.

Adult↗

PubMed1979

Comparison of ejection fraction and segmental circumferential fiber shortening velocity in the anesthetized and conscious canine.

A chronically and transseptally implanted left atrial catheter was utilized to perform repeated cineangiography in the conscious dog. The advantage of this preparation is that catheter placement does not require a thoracotomy. Left ventricular function was compared in the same pentobarbital-anesthetized and conscious dog. Anesthesia significantly depressed myocardial function as was demonstrated by a decrease in ejection fraction and segmental circumferential fiber shortening velocity (VCF) and an increase in end-diastolic volume. In addition, no difference in Vcf occurred between the base and the apex. Since anesthesia produced regional difference in the degree of depression of VCF, we conclude that anesthesia will produce patterns of ventricular contraction which are variable and unpredictable. Consequently, we recommend the use of the conscious dog and this preparation in order to evaluate myocardial function.

Anesthetics↗

PubMed1993

Job turnover and regional attrition among physiotherapists in northern Ontario.

Results of an initial study indicated that the most significant factor affecting retention for Physiotherapists in Northern Ontario was perceived opportunity for career development. A follow-up study was completed two years later to determine: 1) actual job turnover and regional attrition among physiotherapists in Northern Ontario; and 2) the predictive validity of variables identified in the first study regarding job turnover and regional attrition. Job turnover occurred in 29.5% of those sampled and the regional attrition rate was 12%. Discriminant function analysis revealed factors affecting job turnover and regional attrition including professional experience, practice location, opportunity for career development and size of community of residence. Based on previous intention, indicated by participants, follow-up revealed that the initial study correctly predicted 77.5% of those who changed their jobs and 74.1% of those who left Northern Ontario. Identified factors provide direction for the development of strategies for recruitment and retention of physiotherapists.

Adult↗

PubMedDate not supplied

Mapping the functional anatomy of sentence comprehension and application to presurgical evaluation of patients with brain tumor.

BACKGROUND AND PURPOSE: The main clinical indication for functional MR imaging (fMRI) has been to preoperatively map the cortex. Motor paradigms to activate the cortex are simple and robust; however, language tasks show greater variability and difficulty. The aim of this study was to develop a language task with an adequate control task to engage the areas of the posterior temporal lobe responsible for sentence comprehension. METHODS: We performed a cloze paradigm requiring silent reading of a visually presented sentence-completion task based on semantic meaning versus a letter-scanning epoch requiring the completion of nonlinguistic strings or a rest period. Before this task was clinically used in two patients epilepsy and cavernous angioma, its feasibility and accuracy were tested in 14 healthy right-handed participants. RESULTS: Results showed significant activation of the posterior temporal cortex, including a broad area across the posterior left temporal cortex extending into the inferior parietal lobule. When the sentence completion-minus-letter string task was compared with the sentence completion-minus-rest task, increased activation was present in the posterior temporal lobe. CONCLUSION: Decreased significant activation during the sentence completion-minus-rest contrast may be attributed to increased noise from intersubject variability in the rest period. Our results suggest that this task elucidates areas important to reading comprehension in the posterior and inferior temporal regions that verbal fluency and auditory discrimination tasks do not. Data from two cases are summarized to exemplify the input of this task for neurosurgery.

Adult↗

PubMed1984

Echocardiographic features of truncal abnormalities. Special emphasis to the evaluation of pulmonary arteries.

9 patients with persistent truncus arteriosus, 11 patients with pseudotruncus and 2 patients with hemitruncus, ranging in age from 6 months to 29 years, have been studied by M-mode and two-dimensional echocardiography (2-D echo). In all patients the diagnosis was confirmed by cardiac catheterization and angiocardiography; in 10 of them surgical or autopsy documentation was available. Peripheral contrast echocardiography was performed in 13 patients. A variable degree of truncal or aortic override was observed in 7 of 9 patients with truncus arteriosus and in all patients with pseudotruncus by M-mode or two-dimensional echocardiography. By 2-D echo the truncal origin of the right and left pulmonary arteries was visualized in 7 of 9 of the patients with truncus arteriosus. Visualization of one aberrant pulmonary artery from the aortic wall was assessed retrospectively in 2 patients with hemitruncus. A pulmonary atretic valve region was recorded in 10 of 11 of the patients with pseudotruncus. Peripheral contrast echocardiography enabled to distinguish patients with complete obstruction to pulmonary flow from patients with unobstructed right ventricular outflow tract. By showing no direct connection between the pulmonary arteries and the ascending aorta or direct continuity between one or both pulmonary arteries and truncal or aortic root, differentiation of pseudotruncus arteriosus from truncus or hemitruncus may be achieved by 2-D echo.

Adolescent↗

PubMed1980

[Sex, constitutional, and age characteristics of the anatomy of regional gastric lymph nodes in adult humans].

In 80 corpses of mature subjects of both sex anatomy and topography of the main groups of the gastric regional lymph nodes (cardial, left gastric, pyloric, right and left gastro-mesenteric, splenic) have been studied. It has been stated that the lymph nodes in question are greater in size in men than in women. In women an oval and round formes are noted more often than in men, while segmented and ribbon-like nodes are more characteristic for men. Certain peculiar features of the lymph nodes are connected with constitution. It has been stated that number and size of the gastric regional lymph nodes are more variable in mesomorphic subjects. For brachymorphic subjects a great number of oval and round middle sized lymph nodes is a characteristic feature. In dolichomorphic subjects a small number of large lymph nodes is noted most often. Age peculiarities in the anatomy of the human gastric regional lymph nodes have been revealed: in middle-aged and in old persons their number increases, while their size decreased.

Adult↗

PubMed1994

Coronary blood flow autoregulation and flow heterogeneity in the stunned heart.

We used an anesthetized swine model of regionally "stunned" myocardium to determine the effect of stunning on coronary autoregulation and blood flow heterogeneity. In 18 domestic swine, stunning was accomplished by reducing blood flow to the left anterior descending coronary artery (LAD) by approximately 75% of baseline for 15 min and restoring it to normal for 1 hour. We quantified coronary autoregulation using both the slope of coronary pressure-flow curves and an autoregulation index. We quantified blood flow heterogeneity using radioactive microspheres to determine the variability in flow (dispersion index) among forty 200 mg segments of myocardium from the center of the stunned, LAD-perfused left ventricle. Before and after stunning, we measured autoregulation, myocardial blood flow and flow heterogeneity, as well as hemodynamic indices of myocardial oxygen demand. Fifteen min of ischemia and 1 hour of reperfusion produced both a 46% reduction in mechanical function, and a 7% drop in systemic arterial pressure, but not change in heart rate or rate pressure product. Myocardial oxygen consumption was 15% reduced and myocardial blood flow 16% reduced in the stunned myocardium when measured at one hour of reperfusion. Fifteen min after reperfusion, the slope of the coronary pressure flow plots and the coronary venous oxygenation were increased whereas the autoregulation index decreased. These findings all indicate reduced autoregulation during early reperfusion. However, after one hour of reperfusion, the slope of the coronary pressure-flow relation (0.41 +/- 0.19 vs. 0.48 +/- 0.26 ml.100 g-1.min-1.mmHg-1) and the autoregulation index (0.43 +/- 0.16 vs. 0.30 +/- 0.32) were unchanged from control measurements (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Role of thallium-201 and PET imaging in evaluation of myocardial viability and management of patients with coronary artery disease and left ventricular dysfunction.

The reported mortality of patients with coronary artery disease (CAD) and congestive heart failure is high but variable. In the clinical management of these patients, the available treatment choices are medical therapy, cardiac transplantation and myocardial revascularization. Myocardial revascularization has become an attractive alternative in the management of patients with CAD and poor left ventricular function because medical therapy is associated with a high mortality and cardiac transplantation is expensive and not practical due to shortage of donor hearts. Myocardial revascularization, however, should be recommended in those patients in whom the procedure is very likely to reverse regional and global left ventricular dysfunction and to improve heart failure symptoms and survival. Thallium-201 rest-redistribution myocardial scintigraphy and PET imaging of myocardial perfusion and 18F-fluoro-deoxyglucose metabolism have been extensively evaluated for the assessment of myocardial viability and for prediction of recovery of regional left ventricular dysfunction following myocardial revascularization; with positive and negative predictive accuracies of 72% and 70% for 201Tl rest-redistribution imaging and 83% and 84% for perfusion-metabolism PET imaging. Both modalities also are predictive of improvement in left ventricular ejection fraction after myocardial revascularization. Patients with congestive heart failure who demonstrate the PET pattern of mismatch are more likely to improve their heart failure symptoms following revascularization than those without the mismatch pattern. Furthermore, the PET pattern of mismatch identifies a subgroup of patients who are at very high risk for cardiac death on medical therapy. Survival of these patients can be significantly improved by myocardial revascularization.

Coronary Artery Bypass↗