Dan G. Pavel

Chronic Hypoxemia Depresses Global Ventricular Function and Predisposes to the Depletion of High-Energy Phosphates during Cardioplegic Arrest: Implications for Surgical Repair of Cyanotic Congenital Heart Defects

Persistence of impaired ventricular function after repair of cyanotic congenital heart defects may be due to previous exposure to chronic hypoxemia or to perioperative ischemic injury. Clarification of this phenomenon was sought in a canine model of cyanotic cardiovascular disease (Group I), in which the left atrium was anastomosed proximal to the banded pulmonary artery. Animals that had pulmonary artery banding alone (Group II) or no prior surgical intervention (Group III) served as controls. All Group I animals became cyanotic during the study period (arterial oxygen tension, 38 +/- 4 mm Hg; hematocrit, 55 +/- 5%). Radionuclide-determined ejection fractions performed three months after operation showed significant depression of global biventricular function by 16 to 29% (p less than 0.05) compared with groups II and III. On cardiopulmonary bypass, all hearts were subjected to 4 degrees C potassium cardioplegic arrest and reperfusion with serial assays for myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) levels. The ATP and CP stores in each ventricle were similar at all sampling intervals, and preischemic levels were comparable in cyanotic and control groups. However, ATP levels were significantly depressed 37 to 43% from preischemic levels (p less than 0.02) after arrest and reperfusion in cyanotic dogs, but they were preserved in Groups II and III. During ischemia, CP stores were depleted to 27% of preischemic values in Group I but only to 46 to 63% of preischemic levels in the control groups (p less than 0.05). These data indicate that chronic hypoxemia impairs global ventricular function and predisposes to the accelerated depletion of high-energy phosphates during cardioplegic arrest.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythromycin stearate as prokinetic agent in postvagotomy gastroparesis

We describe a patient with severe postvagotomy gastroparesis who failed standard medical therapy but had an excellent clinical and radiological response to 250 mg of erythromycin administered 30 min before each meal. Improvement was further documented by a marked improvement in this patients 99m Tc-sulfur colloid radionuclide gastric emptying scan

Sequential regional phase mapping of radionuclide gated biventriculograms in patients with left bundle branch block

Phase analyses of biventricular radionuclide (RNA) gated studies were carried out in seven patients with normal conduction and in eight patients with left bundle branch block, (LBBB) all without significant abnormalities of hemodynamics or ventricular wall motion. The first Fourier harmonic of time-activity variation in each pixel was computed and displayed as an ampiltude image, a phase image, and a phase distribution histogram. In addition, automatically determined areas of earliest and latest phase for each ventricle were examined and compared. Qualitative analysis revealed relatively uniform distribution of phase across both ventricles in patients with normal conduction, but markedly delayed phase in the left ventricle (LV) of patients with LBBB. In addition, the location within the ventricles of areas of earliest and latest phase was somewhat different for the two groups, the most prominent finding being an area of earliest LV phase along the interventricular septum seen in seven of eight patients with LBBB but in none of the normal conduction patients. Quantitatively, relative measures of mean, early, and late phase calculated by subtracting respective RV from LV values of phase to give ΔMean, ΔEarly, and ΔLate showed marked LV phase delay in LBBB patients. Values of these parameters (normal conduction vs LBBB, mean ± SD) were ΔMean (−5 ± 2 vs 36 ± 9 degrees, p p = 0.0001), and ΔLate (−7 ± 8 vs 35 ± 11 degrees, p

Radionuclide regurgitant index: Value and limitations☆

The radionuclide regurgitant index, defined as left ventricular/right ventricular stroke counts obtained from gated equilibrium studies, has been reported to predict the presence and severity of left-sided valve regurgitation. This study evaluated the radionuclide regurgitant index in 100 patients in whom left-sided valve regurgitation was angiographically graded (0 to 4+) with regard to most severe mitral or aortic regurgitation. Regurgitation was graded 0 in 44 of the 100 patients, 1+ in 22, 2+ in 8, 3+ in 6 and 4+ in 20. The radionuclide regurgitant index was 0.9 to 1.5 in 51 patients, 1.6 to 2.4 in 23 and 2.5 to 12.0 in 26. The mean radionuclide regurgitant index was 1.34 in the group with no regurgitation and 1.60 in those with 1+, 2.01 in those with 2+, 2.80 in those with 3+ and 3.85 in those with 4+ regurgitation. There was a significant difference (p less than 0.05) in the radionuclide regurgitant index between patients with no regurgitation and each group with regurgitation and between groups with regurgitation separated by two or more grades of angiographic regurgitation. Twelve patients had a discordant radionuclide regurgitant index; their index either predicted clinically significant or severe regurgitation when they had no or trivial regurgitation, or predicted no or trivial regurgitation when they had clinically significant regurgitation. Eight of 10 patients with a left ventricular ejection fraction of less than 0.30 had a discordant index (p less than 0.0005). All three patients with mitral valve prolapse associated with frequent ventricular extrasystoles had a discordant index (p less than 0.0005).

An Automatic Threshold-Based Scaling Method for Enhancing the Usefulness of Tc-HMPAO SPECT in the Diagnosis of Alzheimer's Disease

Functional imaging of the brain can aid in the diagnosis of Alzheimer’s disease. Tc-HMPAO SPECT is widely available and relatively inexpensive to use. Combined with computer-based analysis of images, SPECT is a powerful tool in detecting decreases in brain perfusion caused by Alzheimer’s disease. However, analysis can falsely elevate the perfusion of normal areas and diminish the perfusion of atrophic areas in the Alzheimer’s brain when used with conventional scaling methods. In this paper, we present a technique for scaling images that overcomes the problems associated with conventional scaling methods. Our technique was successful in eliminating or attenuating the false increases in perfusion shown in probable Alzheimer’s patients in over 90% of cases (n=17), and in enhancing the sensitivity of detection of degenerative changes by Statistical Parametric Mapping.

Sequential regional phase mapping of radionuclide gated biventriculograms in patients with sustained ventricular tachycardia: Close correlation with electrophysiologic characteristics

Radionuclide (RNA) gated studies were performed during sinus rhythm and during spontaneous or induced sustained ventricular tachycardia (VT) in six patients with clinical VT. Fourier analysis of time-activity variation was used to calculate a RNA phase value for each pixel in the image. Color coding of each pixel according to its calculated phase resulted in a RNA phase map of the ventricles. The following results were considered to be consistent with the known electrophysiology of VT: (1) the phase map correlated with QRS morphology and axis in most but not all tachycardias; (2) earliest phase usually demonstrated the VT origin to be at the border of the ventricular wall motion abnormality; (3) endocardial mapping (available in one patient) showed close correlation with RNA phase mapping; (4) in three patients with ischemic heart disease, VT with left bundle branch block (LBBB) pattern had earliest LV phase along the septum; and (5) for one patient imaged during two different VT morphologies, the tachycardias had earliest phase at different borders of the same wall motion abnormality with differing progression of phase across the ventricles. RNA phase mapping of VT is feasible and appears to provide data consistent with the electrophysiology of this arrhythmia.

Incorporation of SPECT imaging in a longitudinal cognitive rehabilitation therapy programme

In this clinical study, five consecutive referrals to a cognitive rehabilitation therapy (CRT) programme were followed in a longitudinal protocol involving a resting SPECT and neuropsychological evaluation at pre-treatment, post-treatment, and post non-treatment intervals. All clients had acquired brain injury and initially demonstrated neuropsychological deficits and various degrees of hypoperfusion on SPECT. Statistical Parametric Mapping (SPM) was used to evaluate change in successive SPECT images. Following CRT, all clients were able to return to productive employment or schooling. Examination of the neuropsychological testing results revealed significant improvement in performance following CRT which were generally maintained during the non-treatment period. SPM analysis of the SPECT data revealed that, in a majority of cases, most of the significant increases in relative cerebral blood flow redistribution were seen during the treatment period, rather than the non-treatment period. The results suggest that, even in individuals who are more than 2 years post-brain damage, relative increases in rCBF can be demonstrated following individualized CRT and that most of these changes can be related to improvements on neuropsychological tests.

Detection and quantification of regional wall motion abnormalities using phase analysis of equilibrium gated cardiac studies.

Phase images obtained from equilibrium gated cardiac studies were evaluated for qualitative and quantitative information and correlated with contrast angiography in 33 patients. The left ventricular region of interest was obtained by a semiautomatic procedure which avoided underestimation of size but also eliminated extraventricular pixels. Phase images and phase distribution histograms were arranged in three standard displays which included the whole heart, isolated left ventricle, isolated abnormal areas, and quantification of maximum phase shift in the whole free border and in the inferolateral and posterolateral segments. Only the free left ventricular border was evaluated. According to contrast angiography results, four categories were obtained: normal, hypokinetic, akinetic, and dyskinetic. The best correlation with contrast angiography was found with the results obtained by dividing the left ventricular free border in two segments (r = 0.91). Scheffes test for multiple comparisons showed significant differences between each of the four categories. Expressed in phase shifts from the histogram mode, the lower limits for the three abnormal categories were established at 30°, 78°, and 156° respectively for hypokinetic, akinetic, and dyskinetic segments. For distinguishing normal from abnormal segments, sensitivity = 83%, specificity = 94%, and accuracy = 89%. The main reasons for discrepant results appeared to be small hypokinetic areas in an otherwise normal ventricle, very large area of hypokinesia, segments adjacent to an area of marked abnormality, and ventricles with asynchrony (wave-like motion). The method described provides an image which characterizes myocardial synchrony, generates clear boundaries for abnormal areas, and lends itself to quantification.

Assessment of left ventricular function by radionuclide angiography during induced supraventricular tachycardia

Electrocardiographically synchronized radionuclide angiography was performed before, during and after induced paroxysmal supraventricular tachycardia in 13 patients. Data were acquired with a computer-interfaced Anger camera in a left anterior oblique projection. No data were acquired during tachycardia until tachycardia had been sustained for 1 minute. Patients ranged in age from 20 to 64 years (mean +/- standard deviation 42 +/- 14.5). Three patients had organic heart disease and 10 did not. Baseline and tachycardia heart rates (beats/min) were 59 to 99 (73 +/- 11) versus 141 to 228 (157 +/- 22). Baseline and tachycardia left ventricular measurements (mean +/- standard error) were as follows: ejection fraction 64 +/- 2 versus 62 +/- 4 percent (not significant), ejection rate 3.0 +/- 0.1 versus 4.3 +/- 0.4 mean ventricular counts/s (p less than 0.001), normalized end-diastolic counts 72.7 +/- 7.8 versus 48.7 +/- 6.7 X 10(3) counts (p less than 0.001), normalized stroke counts 37.1 +/- 3.4 versus 23.3 +/- 2.7 X 10(3) counts (p less than 0.001) and normalized count cardiac output 2,717.5 +/- 273.0 versus 3,620.2 +/- 403.7 X 10(3) counts/min (p less than 0.005). Although ejection fraction for the whole group did not change significantly, it decreased during tachycardia by 5 percentage points or more in five patients. These were the three patients with heart disease and the two normal patients with the fastest heart rate during tachycardia (228 and 214 beats/min, respectively). In summary, paroxysmal supraventricular tachycardia was characterized by a marked decrease in left ventricular end-diastolic and stroke volumes but increased ejection rate and cardiac output without significant change in ejection fraction. Heart disease or rapid heart rate during tachycardia appeared to have a deleterious effect on ejection fraction.

Indium 111-labeled granulocyte scan in the diagnosis and management of acute inflammatory bowel disease

The indium 111 granulocyte scan was used to evaluate 39 individuals known to have or suspected of having inflammatory bowel disease. Twenty-three of these individuals had positive scans and 16 had negative scans. Eighty-seven confirmatory studies, which consisted of barium radiography, endoscopy, operative findings, and histopathology, were performed in 37 of these individuals. The remaining two negative scans corroborated only by clinical course, CBC, and erythrocyte sedimentation rate. In addition, 10 follow-up scans were performed in six of the 39 patients to monitor therapy or investigate a change in symptoms. As an anatomic indicator of acute granulocytic infiltration of the intestinal lamina propria and crypts, the authors found that this scan had a 97 percent rate of sensitivity and 100 percent specificity. Specific indications for the use of the indium 111-labeled granulocyte scan are described. For the authors, in general, this test has become a vital adjunct to endoscopy and radiography in the diagnosis and management of patients with symptoms of inflammatory bowel disease.