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J Krivokapich

Publications and source records attributed to J Krivokapich.

54 records · Page 3Linked to original sources
PubMed1986

Regional myocardial metabolism in patients with acute myocardial infarction assessed by positron emission tomography.

Positron emission tomography has been shown to distinguish between reversible and irreversible ischemic tissue injury. Using this technique, 13 patients with acute myocardial infarction were studied within 72 hours of onset of symptoms to evaluate regional blood flow and glucose metabolism with nitrogen (N)-13 ammonia and fluorine (F)-18 deoxyglucose, respectively. Serial noninvasive assessment of wall motion was performed to determine the prognostic value of metabolic indexes for functional tissue recovery. Segmental blood flow and glucose utilization were evaluated using a circumferential profile technique and compared with previously established semiquantitative criteria. Relative N-13 ammonia uptake was depressed in 32 left ventricular segments. Sixteen segments demonstrated a concordant decrease in flow and glucose metabolism. Regional function did not change over time in these segments. In contrast, 16 other segments with reduced blood flow revealed maintained F-18 deoxyglucose uptake consistent with remaining viable tissue. The average wall motion score improved significantly in these segments (p less than 0.01), yet the degree of recovery varied considerably among patients. Coronary anatomy was defined in 9 of 13 patients: patent infarct vessels supplied 8 of 10 segments with F-18 deoxyglucose uptake, while 10 of 13 segments in the territory of an occluded vessel showed concordant decreases in flow and metabolism (p less than 0.01). Thus, positron emission tomography reveals a high incidence of residual tissue viability in ventricular segments with reduced flow and impaired function during the subacute phase of myocardial infarction. Absence of residual tissue metabolism is associated with irreversible injury, while preservation of metabolic activity identifies segments with a variable outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Identification of impaired metabolic reserve by atrial pacing in patients with significant coronary artery stenosis.

We investigated myocardial 11C-palmitate clearance kinetics at a resting heart rate (control) and during pacing using positron-emission tomography in 10 patients with significant coronary artery stenosis (greater than 70%) and evidence of exercise-induced ischemia. Serial 11C-palmitate images acquired at control and during pacing revealed biexponential myocardial 11C clearance both in myocardium supplied by a stenotic coronary artery (myocardium "at risk") and in myocardium supplied by a normal coronary artery (normal myocardium). At control, the average rate of myocardial 11C clearance from the early rapid curve component (the clearance half-time) was similar in normal myocardium and in that at risk (22.2 +/- 5.2 vs 21.0 +/- 5.4 min, NS), as was the amount of myocardial 11C activity at the end of the early rapid phase (residual fraction 56.3 +/- 7.2% vs 54.7 +/- 7.3%, NS). Thus, myocardial clearance was homogeneous at control, suggesting a similar rate and amount of 11C-palmitate oxidation in normal myocardium and in that at risk. Pacing shortened clearance half-times and decreased residual fraction in both normal myocardium and that at risk compared with control. However, clearance half-times were 17% longer and residual fractions 14% higher in myocardium at risk compared with normal myocardium (p less than .005 and p less than .01, respectively). Therefore, during pacing myocardial 11C clearance became heterogeneous, suggesting impaired 11C-palmitate oxidation in myocardium at risk compared with normal myocardium. Increased substrate utilization in response to increased workload can be thought of as a measure of metabolic reserve. Our data suggest metabolic reserve for free fatty acid oxidation is impaired in myocardium supplied by a significantly stenosed coronary artery and that this impairment can be detected by analysis of myocardial 11C-palmitate clearance.

Adult↗
PubMed1985

Effects of anoxia and ischemia on thallium exchange in rabbit myocardium.

We investigated the effects of anoxia and ischemia on thallium (201Tl) exchange using isolated rabbit interventricular septa. Anoxia for 20 or 40 min caused a decrease in 201Tl tissue uptake due to an increased efflux of 201Tl with a smaller increase in 201Tl influx. Between 40 and 60 min of anoxia, the increased efflux of 201Tl was reversed and the increase in 201Tl influx was absent. After 60 min of reoxygenation, septa made anoxic for 20-60 min recovered at least 95% of the Tl lost. Mechanical recovery, however, was still significantly depressed. Reperfusion after total ischemia for 20-60 min was followed by resumption of 201Tl uptake despite continued mechanical dysfunction. Efflux rates during reperfusion after ischemia were significantly different from preischemic values but not in a predictable way. This unpredictability complicates interpretation of clinical 201Tl redistribution studies. These results represent important differences from those reported previously using 42K [Am. J. Physiol. 232 (Heart Circ. Physiol. 1): H85-H94 and H564-H570, 1977]. Anoxia did not increase the influx of 42K. Also, 60 min of ischemia resulted in progressive losses of 42K. This implies there are different sensitivities and/or mechanisms for Tl compared with K uptake. Our results are consistent with 201Tl uptake by severely damaged and nonviable cells.

Animals↗
PubMed1984

Kinetic characterization of 13NH3 and [13N]glutamine metabolism in rabbit heart.

The isolated arterially perfused rabbit interventricular septum was used to study the effects of methionine sulfoximine (MSO) on 13N-labeled ammonia (13NH3) and 13N-labeled glutamine [( 13N]gln) metabolism. Tissue time-activity curves were generated from bolus injections of 13NH3 or [13N]gln delivered interarterially during control conditions and in the presence of MSO. The fraction of 13N label retained in the tissue [EF(3)] was significantly (P less than 0.01) less after a bolus of [13N]gln than 13NH3. MSO significantly (P less than 0.05) decreased the EF(3) after a bolus of 13NH3 or [13N]gln. Chemical analyses using high-pressure liquid chromatography on tissue and effluent samples obtained after bolus injections of 13NH3 and [13N]gln with or without MSO present showed the following: 1) after a bolus of 13NH3 or [13N]gln the tissue 13N label is predominantly in [13N]gln at 6 min after injection, and 2) MSO significantly decreases the synthesis of [13N]gln after an 13NH3 bolus. Thus it would appear that the glutamine synthetase reaction is primarily responsible for the retention of the 13N label from 13NH3 as [13N]gln in rabbit myocardium.

Ammonia↗
PubMed1983

Aortic valve systolic flutter as a screening test for severe aortic stenosis.

Previous efforts using M-mode echocardiography or 2-dimensional (2-D) echocardiography have not consistently separated patients with and without significant aortic stenosis (AS). We postulated that an aortic valve sufficiently pliant to produce systolic flutter on M-mode echocardiography could exclude significant AS and reviewed the M-mode echocardiograms of 50 consecutive patients (mean age 59 years) catheterized for presumed AS; 2-D echocardiography was also performed in 18 of 50 patients (36%). In 40 of 50 patients (80%) the aortic valve cusps were easily identified on M-mode echocardiography: 19 of 40 (48%) had systolic flutter with a mean aortic valve gradient of 4 +/- 8 mm Hg (mean +/- standard deviation [SD]) and an aortic valve area of 2.8 +/- 0.4 cm2; 21 of 40 (52%) had no systolic flutter with a mean aortic valve gradient of 55 +/- 19 mm Hg and an aortic valve area of 0.7 +/- 0.3 cm2. In the 10 of 50 patients (20%) in whom aortic valve cusps were not clearly identified, the mean aortic valve gradient was 50 +/- 24 mm Hg and the aortic valve area 0.8 +/- 0.4 cm2. Systolic flutter was not seen with an aortic valve gradient greater than 30 mm Hg or an aortic valve area less than 1 cm2. Aortic valve systolic opening by M-mode echocardiography or 2-D echocardiography did not accurately predict the severity of AS. Thus, aortic valve systolic flutter seen on M-mode echocardiography is strong evidence against significant AS, but the absence of systolic flutter does not allow reliable prediction of the severity of AS. The finding of systolic flutter by M-mode echocardiography may be a useful screening test in patients presumed to have AS.

Aortic Valve↗
PubMed1982

Dependence of 13NH3 myocardial extraction and clearance on flow and metabolism.

The isolated arterially perfused rabbit interventricular septum was used to study the relationship between flow (F) and myocardial uptake and subsequent clearance of bolus injections of 13N-labeled ammonia (13NH3). Multiple 13NH3 injections were delivered to a total of 19 septa at perfusion rates (F/g) ranging from 0.2-4.0 ml.min-1.g-1. Ten septa were studied at 37 degrees C and nine were studied at 28 degrees C to obtain uptake and clearance data at different metabolic rates. The septa were perfused without recirculation with a modified Tyrode solution. Analysis of the time-activity curves generated by the injections of 13NH3 revealed that the data was best described by three components. The first two components exhibited short clearance times (t1/2s less than 7 min) in contrast to prolonged clearance times (30-500 min) for component 3. Component 1 was consistent with a freely diffusible 13NH3 compartment. Component 3 persists and permits myocardial imaging 15 min or more after 13NH3 injection. At each perfusion rate the extraction fraction of component 3 was twice as large, and the clearance time of component 3 was twice as fast at 37 as at 28 degrees C, implying that the extraction and washout of this third component are dependent on enzymatic reactions. The total myocardial extraction into component 3 from a systemic injection is determined by multiplying the extraction fraction by the perfusion rate (EF(3) X F/g) and was directly related to the perfusion rate at both 28 and 37 degrees C.

Ammonia↗
PubMed1982

Estimation of rabbit myocardial metabolic rate for glucose using fluorodeoxyglucose.

The isolated arterially perfused rabbit interventricular septum was used to determine the feasibility of using the glucose analogue 18F-2-deoxy-2-fluoro-d-glucose (DG) with a tracer kinetic model to estimate the rate of exogenous glucose utilization. FDG was delivered to the septum by constant infusion, and tissue 18F radioactivity was measured as a function of time by external coincidence counting. The following four conditions were studied: flow rates of 0.5, 1.0, and 1.5 ml/min with a heart rate of 72 beats/min and flow at 1.5 ml/min with 96 beats/min. The rate constants for FDG forward and reverse transport between the vascular and extravascular compartments (k*1, k*2, respectively), phosphorylation of FDG (k*3), and dephosphorylation of FDG-6-phosphate (FDG-6-P) (k*4) were determined from the tissue curves using a tracer kinetic model. The lumped constant (LC) of the deoxyglucose model calculated using Fick-derived myocardial metabolic rates of glucose (MMRGlc), was 0.60 +/- 0.10 and was stable over the range of conditions studied. Average k*'s and LC were used to calculate MMRGlc's employing the model and were not significantly (P greater than 0.05) different from those determined by the Fick method. Tissue analyses using high-pressure liquid chromatography documented that tissue 18F radioactivity wa due to FDG and FDG-6-P, and their relative fractions agreed well with the values predicted from the tracer kinetic model. Only FDG was detected in the effluent. These studies also indicate the presence of a myocardial enzyme that can hydrolyze FDG-6-P to FDG. Thus our results support the use of the FDG method with positron-computed tomography for the in vivo determination of the myocardial rate of exogenous glucose utilization.

Animals↗
PubMed1982

Pericardial disease in familial Mediterranean fever: an echocardiographic study.

We studied 30 randomly selected patients with familial Mediterranean fever (FMF) by M mode echocardiography to determine the frequency of pericardial involvement. There was no evidence of congestive heart failure, uremia, or any other illness known to be associated with pericardial disease in the study population. Eight of the 30 patients (27 percent) had echocardiographic evidence of pericardial disease. Two had pericardial effusions, two had pericardial thickening, and four either or both. Patients with pericardial involvement had a mean duration of FMF of 28.9 +/- 12.2 (SD) years vs 18.5 +/- 10.6 (SD) years for those without pericardial disease (P less than .02). We concluded that pericardial involvement is common in FMF and that its occurrence as detected by echocardiography increases with duration of illness.

Adolescent↗
PubMed1982

Mitral valve prolapse. Cross sectional and provocative M-mode echocardiography.

False-negative supine M-mode echocardiograms occur in some patients with proved mitral valve prolapse. To investigate further, we performed M-mode echocardiography (MME) during standing and after the inhalation of amyl nitrite in 17 patients (group 1) selected for auscultatory evidence of mitral valve prolapse (MVP) but negative supine MME. To validate the standing MME technique, eight patients with classic auscultatory MVP with positive supine MME for MVP (group 2) and 15 control subjects (group 3) were studied. Supine cross-sectional echocardiography (CSE) was compared to MME in all three groups. Standing MME elicited echocardiographic evidence of MVP in 14/17 (82 percent) of group 1--auscultatory evidence of MVP but negative supine MME; CSE demonstrated MVP in 8/13 (62 per cent) of the same patients. There was no clear advantage of the CSE long axis view over the CSE apical four chamber view in the diagnosis of MVP in these selected subjects; however, the two views were complementary. Amyl nitrite was ineffective in eliciting echocardiographic evidence of MVP.

Adult↗
PubMed1981

M-mode and cross-sectional echocardiographic diagnosis of right ventricular cavity masses.

Two patients with metastatic carcinoma (one cervical and one testicular) in whom echocardiography was instrumental in diagnosing a right ventricular cavity mass are presented. In first case the M-mode echocardiogram revealed dense echoes in the right ventricle and right ventricular outflow tract during systole and diastole. Surgical confirmation of the mass lesion was obtained. The second case also revealed abnormal echoes in the right ventricle and right ventricular outflow tract, but they were less dense and distinct. Two-dimensional echocardiography clearly delineated a highly mobile mass of tissue in the right ventricle which corresponded to the necropsy findings.

Adult↗
PubMed1981

Mitral valve A wave and mitral stenosis.

We examined M-mode echocardiograms on 35 patients with catheterization-proven mitral stenosis and normal sinus rhythm to determine whether the presence or absence of an A wave on the mitral echogram predicted mild versus severe mitral stenosis. Mitral valve area (MVA) was determined by the Gorlin formula. Presence of a mitral A wave was defined as 2 mm or greater anterior motion (after a well-defined F point) of the anterior mitral leaflet. In six of 35 patients, the presence of an A wave was equivocal. Of the remaining 29 patients, 16 had no A wave and mean MVA = 1.18 cm2 +/- 0.45 (SD), and 13 patients had a definite A wave and mean MVA = 2.04 cm2 +/- 0.71. There was a significant difference (p less than 0.001) between the mean MVA for patients with and without definite A waves. No patients with a definite A wave had an MVA less than 1.2 cm2. An A wave on the mitral echogram (in sinus rhythm) excludes severe mitral stenosis; when an A wave is not seen, no definite statement concerning severity of mitral stenosis can be made.

Adult↗
PubMed1981

Effect of left ventricular size on mitral E point to ventricular septal separation in assessment of cardiac performance.

Increased mitral valve E point to ventricular septal separation (EPSS) is widely used as an echocardiographic index of depressed left ventricular (LV) ejection fraction (EF), yet LV size has not been examined as an independent variable potentially affecting EPSS. Accordingly, we studied end-diastolic dimensions (EDD). Twenty normal controls had EPSS 3.2 +/- 2.2 mm (mean +/- SD), EDD 47 +/- 5 mm, EPSS/EDD ("normalized" EPSS) 0.07 +/- 0.04, and fractional shortening (FS%) 38 +/- 6%. Nine patients with pure chronic mitral regurgitation had dilated LV (EDD = 65 +/- 7 mm) with normal LV function (FS% 41 +/- 5%; angiographic EF 62 +/- 9%); eight patients had dilated cardiomyopathy (EDD 69 +/- 8 mm) with decreased LV function (FS% 16 +/- 7%; angiographic EF 32 +/- 8%); and eight patients with amyloid cardiomyopathy had nondilated LV (EDD 42 +/- 5 mm) with decreased LV function (FS% 19 +/- 6; angiographic EF 35 +/- 7%). Mitral E point to ventricular septal separation and EPSS/EDD accurately separated individuals with normal and abnormal LV function irrespective of LV size (chi 2 = 36.7; p less than 0.00001). Increased internal dimensions per se did not affect EPSS unless depressed LV function coexisted. EPSS is therefore a valid predictor of depressed ejection phase indices independent of LV size.

Adult↗
PubMed1981

Effects of hyperkalemia and glycoside on thallium exchange in rabbit ventricle.

The exchange characteristics of thallium-201 (201Tl) were studied using the isolated arterially perfused rabbit interventricular septum to gain insight into the mechanisms that govern its uptake and subsequent washout from myocardial tissue. The results were compared to potassium-42 (42K) exchange. Unlike 42K, the uptake and tissue washout exchange rates for 201Tl were not equal. The 201Tl washout exchange rate was slower than that for the uptake. Hyperkalemia increased the efflux of both 42K and 201Tl, but the increase in 201Tl efflux was not due to an increase in permeability, as was true for 42K, but to a hyperkalemia, induced increase in compartment size of exchangeable 201Tl. Acetylstrophanthidin (ACS) resulted in an increase in 201 Tl efflux similar to the increase in 42K efflux seen with ACS. However, ACS did not inhibit 201Tl influx, in contrast to the known inhibition of 42K influx. This indicated that influx of tracer amounts of 201Tl was not dependent on the sodium-potassium pump. A model of Tl exchange in rabbit ventricles is proposed.

Animals↗
PubMed1980

Flail aortic valve leaflets: M-mode and two-dimensional echocardiographic manifestations.

Four patients with documented flail aortic valve leaflets were studied using M-mode and two-dimensional echocardiography (2-D echo). Two had aortic valve endocarditis, one had endocarditis involving a congenital heart defect, and one had a myxomatous aortic valve. Mitral valve flutter and early mitral valve closure led to the diagnosis of severe aortic insufficiency in three patients. Diastolic aortic valve flutter, considered to be specific for a flail aortic leaflet, was present in three patients. In the fourth patient left ventricular outflow tract (LVOT) echoes were present, but did not distinguish between a flail aortic leaflet and an aortic vegetation. Two-D echo confirmed LVOT echoes in all patients. Discrimination between a flail leaflet and a vegetation(s) without leaflet disruption was accomplished by noting the hinge point of the LVOT diastolic echoes, which was the aortic wall in patients with a flail leaflet. The combination of these M-mode and 2-D echocardiographic findings permitted the diagnosis of a flail aortic leaflet to be made accurately and noninvasively. In two patients surgery was performed without prior cardiac catheterization.

Adolescent↗
PubMed1979

M mode and cross-sectional echocardiographic features of flail posterior mitral leaflets.

Seventeen patients with accepted M mode echocardiographic criteria for flail mitral leaflet were studied. M mode echocardiograms revealed characteristic disordered mitral valve motion: (1) 16 (94 percent) had chaotic diastolic mitral motion; (2) 14 (82 percent) had systolic mitral flutter; (3) 14 (82 percent) had systolic left atrial echoes; and (4) 12 (71 percent) had systolic mitral valve prolapse. In 8 patients (47 percent) all four findings were present, with three findings present in 16 (35 percent) and two findings present in 13 (18 percent); none had fewer than two findings. Cross-sectional echocardiographic studies in 10 patients revealed a systolic whipping motion of the posterior mitral leaflet into the left atrium in all, abnormal systolic mitral coaptation in all and an abnormal mass of systolic left atrial echoes in 4. None of the first three M mode criteria were observed in 230 patients with uncomplicated "mid systolic click-late systolic murmur" syndrome; cross-sectional echocardiography in 30 of 230 patients revealed normal systolic mitral coaptation and no systolic whipping of the tip of the posterior mitral leaflet into the left atrium.

Adolescent↗
PubMed1979

Increased right ventricular wall thickness on echocardiography in amyloid infiltrative cardiomyopathy.

In six patients with clinically significant amyloid infiltrative cardiomyopathy, echocardiographic right ventricular anterior wall thickness was significantly increased (mean 7.5 +/- 2.3 mm; range 5 to 10 mm). This finding in conjunction with the previously described abnormalities of the left ventricle (symmetric increase in wall thickness, diffuse hypokinesia, and small to normal left ventricular diastolic dimension) is consistent with the findings of a diffuse myocardial infiltrative process and should minimize confusion with constrictive pericarditis.

Adult↗