Blood Pool Method Research Articles

Comparative Evaluation of Thermodilution and Gated Blood Pool Method for Determination of Right Ventricular Ejection Fraction at Rest and during Exercise

Background: Since the development of a Swan-Ganz thermodilution ejection fraction catheter several studies have been published which compare this technique for obtaining right ventricular ejection fraction (RVEF_TD) with alternative methods. However, the reliability of RVEF_TD measurements under exercise conditions remains undetermined. Therefore, the aim of the present study was a comparative evaluation of RVEF_TD with the established gated blood pool method (RVEF_GBP) under exercise conditions. Methods and Results: Twenty-two patients with different cardiac diseases underwent right heart catheterization, including RVEF_TD and simultaneous RVEF_GBP determination at rest and during supine bicycle exercise. Linear regression analysis showed a significant correlation between RVEF_TD and RVEF_GBP at rest (r = 0.73, p ≤ 0.0005) and during exercise (r = 0.74, p ≤ 0.0005). A Wilcoxon analysis showed a high probability of agreement of RVEF_TD and RVEF_GBP at rest and exercise (level of significance for error of the 0 hypothesis of 95.9/73.3%). Conclusion: The thermodilution ejection fraction catheter provides a useful device for reliable, repetitive and safe RVEF measurements, not only at rest but also under exercise conditions. This seems to be clinically important, because by it means RVEF, as a sensitive parameter of primary or secondary right ventricular dysfunction, can be determined in the course of standard right heart catheterization.

10.56 A comparative evaluation of gated blood pool and thermodilution method for determination of right-ventricular ejection fraction at rest and during exercise

10.56 A comparative evaluation of gated blood pool and thermodilution method for determination of right-ventricular ejection fraction at rest and during exercise

Modulation of venous tone in heart failure

Venodilatation may be an important property in drugs used to treat heart failure. Deductions about venous tone from standard hemodynamic studies may be misleading since filling pressures may be reduced by improved left ventricular function. To study the venodilator properties of drugs, we have modified a radionuclide blood pool method and shown that venous volume is increased by 10% after glyceryl trinitrate but is unchanged after the arteriolar dilator hydralazine. In patients with congestive cardiac failure, the calcium channel blocker, felodipine, causes a marked reduction in systemic vascular resistance and left ventricular filling pressures, but venous volume remains unchanged. In a similar group of patients comparable arterial and central effects are seen after the administration of captopril, but venous volume increases by 16%, and this increased venous volume is sustained after 3 months of long-term treatment. Milrinone has been used to treat both acute and chronic heart failure. As expected of a phosphodiesterase inhibitor, it exhibits inotropic properties in animals and humans and also causes arterial vasodilatation. We have studied its effects on venous tone in 10 patients with severe heart failure (New York Heart Association classes III to IV). Milrinone was given intravenously at a loading dose of 50 micrograms/kg followed by an infusion of 0.5 micrograms/kg/min. After treatment, cardiac index, which was measured by thermodilution, increased from 1.8 +/- 0.48 to 2.3 +/- 0.65 L/min/m2 (p less than 0.001); pulmonary artery wedge pressure fell from 23 +/- 6 to 11 +/- 5 mm Hg (p less than 0.001); and systemic vascular resistance index decreased from 4296 to 3168 dynes.sec.cm-5/m2 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Isosorbide dinitrate and glyceryl trinitrate: Demonstration of cross tolerance in the capacitance vessels

Cross tolerance to the arterial effects of sublingual glyceryl trinitrate (GTN) has been demonstrated in subjects taking oral isosorbide dinitrate (ISDN). To determine if cross tolerance also develops in the venous system, the effects of 0.6 mg of GTN on venous capacitance were assessed before (stage A) and during (stage B) therapy with ISDN. Venous capacitance was assessed using the radionuclide blood pool method, with relative changes in regional blood volume measured in the forearm in 6 patients and the splanchnic circulation in 4 patients. Heart rate, blood pressure and blood volume were measured before and at 1-minute intervals for 10 minutes after GTN; there was less than 2% variability in regional blood volume during 6 control measurements. During stage A, 5 minutes after GTN, systolic blood pressure (mean ± standard deviation) decreased by 14% (from 125 ± 15 to 107 ± 19 mm Hg, p < 0.01) and heart rate increased by 17% (from 68 ± 14 to 80 ± 17 beats/min, p < 0.001), while regional blood volume increased to 101 ± 2% at 1 minute (difference not significant [NS]), 111 ± 2% at 5 minutes (p < 0.001) and 107 ± 3% at 10 minutes (p < 0.01) relative to baseline measurements. During stage B, 5 minutes after GTN, systolic blood pressure decreased by only 7% (from 120 ± 10 to 112 ± 10 mm Hg, p < 0.05) and heart rate increased by 7% (from 70 ± 12 to 75 ± 12 beats/min, p < 0.05), while regional blood volume was 100 ± 1 % at 1 minute (NS), 103 ± 1 % at 5 minutes (p < 0.05) and 101 ± 1 % at 10 minutes (NS) after GTN. The changes in blood pressure, heart rate and regional blood volume after GTN during stage B were all significantly less than those observed during stage A. Thus, partial but significant cross tolerance between ISDN and GTN develops in both the arterial and venous systems.

Improved Cardiovascular Hemodynamics with Atrioventricular Sequential Pacing Compared with Ventricular Demand Pacing

To determine the advantages of atrioventricular (AV) sequential pacing over ventricular demand pacing, paired cardiovascular hemodynamic studies were performed in each pacing mode at a constant heart rate. The paired studies included determination of ejection fraction (EF) by echocardiography and gated blood pool radionuclide scanning, and of cardiac output (CO) by the indicator-dilution method. There was no significant difference in EF with either pacing mode. Determined by echocardiography, EF with AV sequential pacing was 57% compared with 56% with ventricular demand pacing; by the gated blood pool method, EF with AV sequential pacing was 58% compared with 57% in the ventricular mode. Significant improvement with AV sequential pacing was seen in CO (4.75 L/min from 3.75 L/min; p < 0.01); stroke volume (58 ml from 48 ml; p < 0.02); arteriovenous oxygen content difference (4.9 vol% from 5.6 vol%; p < 0.01); total peripheral resistance (1,724 dynes sec cm -5 from 2,025 dynes sec cm -5; p < 0.01); and cardiac contractility, as reflected by mixing time (6.9 seconds from 8.0 seconds; p < 0.02). No significant changes were noted in mean arterial or atrial pressure or in systemic oxygen consumption. In a second group of 6 patients, similar paired studies were done in AV sequential pacing modes before and after therapeutic reduction of total peripheral resistance. A significant increase in CO (43%) was observed following reduction in total peripheral resistance. We conclude that AV sequential pacing improves CO more effectively than ventricular demand pacing. Cardiac output can be further enhanced in patients with congestive heart failure by pre-treatment with agents to reduce total peripheral resistance.

Regression of left ventricular hypertrophy from systemic hypertension by enalapril

Reversal of left ventricular (LV) hypertrophy with medical therapy has been studied increasingly in patients with systemic hypertension. However, serial changes of LV function are not found during reversal of LV hypertrophy in hypertensive patients. Seven patients with LV hypertension were studied to evaluate serial changes of LV mass and function after the initiation of the new converting enzyme inhibitor MK-421. LV mass and function were determined serially at the end of a placebo period and at 5 days, 1 month, 3 months and 7 months after the initiation of MK-421, using both 2-dimensional (2-D) guided M-mode echocardiography and radionuclide techniques. All patients except 1 had LV hypertrophy and all had normal LV function (ejection fraction derived from gated blood pool method ∗>49%). There was an inverse relation between LV fractional shortening (percent FS) and end-systolic stress before medication (r = −0.81,p <0.05). LV mass decreased significantly at 3 months and at 7 months (−10%, p < 0.05, and −12%, p < 0.01, respectively) accompanied with persistent decrease of mean blood pressure, which occurred as early as 5 days after start of therapy (133 ± 5 mm Hg at control, to 112 ± 4 mm Hg at day 5). During reversal of LV hypertrophy, the inverse correlation between FS and end-systolic stress remained significant (r = −0.80 to −0.95, p <0.025 for all), with no difference from the placebo period and from this relation in the normal group. Moreover, percent FS, ejection fraction and stroke index remained unchanged. Thus, LV hypertrophy in patients with systemic hypertension can be reversed without deterioration of LV function. Moreover, overall LV function is likely to be determined by afterload even after reversal of LV hypertrophy.

The value of radionuclide angiography as a predictor of perioperative myocardial infarction in patients undergoing abdominal aortic aneurysm resection.

To define the group of patients at high risk for myocardial infarction (MI) and death associated with abdominal aortic aneurysm repair, resting gated blood pool studies were obtained on 50 such aneurysm patients preoperatively. The results indicated that three groups could be distinguished among these patients by cardiac ejection fraction. Group I (n = 25) had preoperative ejection fractions ranging from 56% to 85%. None of the patients in group I suffered an acute perioperative MI. Group II (n = 20) comprised patients with ejection fractions ranging from 36% to 55%. There was a 20% incidence of MI in group II but no cardiac deaths. Group III included five patients with ejection fractions ranging from 27% to 35%. There was an 80% incidence of perioperative MI in these patients, with one cardiac death and one cardiac arrest. All perioperative MIs occurred within the first 48 hours after surgery. In addition there was a 50% incidence of perioperative MI among all those patients who were 80 years of age or older. These results indicate guidelines for the management of patients undergoing abdominal aortic aneurysm repair based on their preoperative ejection fraction. The data further suggest that the noninvasive gated blood pool method of determining ejection fraction may serve a more broadly useful function in helping to determine which of those patients about to undergo major surgical procedures are at high risk for perioperative MI.

The value of radionuclide angiography as a predictor of perioperative myocardial infarction in patients undergoing abdominal aortic aneurysm resection

To define the group of patients at high risk for myocardial infarction (MI) and death associated with abdominal aortic aneurysm repair, resting gated blood pool studies were obtained on 50 such aneurysm patients preoperatively. The results indicated that three groups could be distinguished among these patients by cardiac ejection fraction. Group I (n = 25) had preoperative ejection fractions ranging from 56% to 85%. None of the patients in group I suffered an acute perioperative MI. Group II (n = 20) comprised patients with ejection fractions ranging from 36% to 55%. There was a 20% incidence of MI in group II but no cardiac deaths. Group III included five patients with ejection fractions ranging from 27% to 35%. There was an 80% incidence of perioperative MI in these patients, with one cardiac death and one cardiac arrest. All perioperative MIs occurred within the first 48 hours after surgery. In addition there was a 50% incidence of perioperative MI among all those patients who were 80 years of age or older. These results indicate guidelines for the management of patients undergoing abdominal aortic aneurysm repair based on their preoperative ejection fraction. The data further suggest that the noninvasive gated blood pool method of determining ejection fraction may serve a more broadly useful function in helping to determine which of those patients about to undergo major surgical procedures are at high risk for perioperative MI.

Can right ventricular performance be assessed by equilibrium radionuclide ventriculography?

Although right ventricular function may be examined by following the passage (first pass) of a bolus of radionuclide through the right heart before it reaches the left heart, the counts detected with conventional gamma cameras in such a short time interval are low; moreover, repeated determinations would result in an unacceptable radiation burden to the patient. We have modified the gated equilibrium blood pool method to allow repeated assessment of the right ventricular ejection fraction (RVEF) and have compared the results with the first-pass method in 43 patients. Good agreement was obtained between the two methods (r = 0.91, p less than 0.001). The mean difference between the two methods was 0.04 with an intra-observer variation for the equilibrium studies of 0.03 and an inter-observer difference of 0.04. The mean difference in RVEF for seven patients studied on two separate occasions 30 minutes apart was only 0.02. In four patients the mean RVEF measured at rest was 0.44 +/- 0.05 (SEM) and after exercise it was 0.48 +/- 0.06. After infusion of isoprenaline at 1 microgram/min the mean rose to 0.64 +/- 0.04 (p less than 0.02) and after infusion of a new beta 1-sympathomimetic agent, prenalterol, at doses of 1 and 2 mg it was 0.56 +/- 0.02 (p less than 0.02) and 0.59 +/- 0.03 (p less than 0.01) respectively, where the significance levels are relative to the resting values. In nine patients with good ventricular function the vasodilator nifedipine caused right and left ventricular ejection fractions to increase by the same amount; while in six patients with severe impairment of left ventricular function due to ischaemic heart disease the RVEF increased from 0.58 +/- 0.03 to 0.73 +/- 0.03 (p less than 0.01) after 2 mg of prenalterol, but the left ventricular ejection fraction increased only from 0.22 +/- 0.04 to 0.26 +/- 0.04. We conclude that repeated estimation of right ventricular performance is possible by equilibrium radionuclide ventriculography.

A radionuclide method for the simultaneous study of the effects of drugs on central and peripheral haemodynamics.

Abstract 1 The central and peripheral cardiovascular effects of hydralazine and glyceryl trinitrate (GTN) have been contrasted using radionuclide techniques. 2 Following intravenous injection of technetium-99m labelled human serum albumin, radionuclide ventriculography was performed by the equilibrium blood pool method using a mobile gamma camera. Simultaneous measurements of `peripheral venous volume' were made using a collimated scintillation probe positioned above the patient's calf. 3 Ten patients with angina pectoris were studied at rest, after sublingual administration of 0.5 mg GTN and after intravenous administration of 10 mg hydralazine. 4 GTN caused a mean reduction in the end diastolic volume of the left ventricle of 14.6% ± 4.5% (P < 0.005) but ejection fraction increased by 0.034 ± 0.007 (P < 0.005) so that stroke volume was only reduced by 4.9% ± 5.0% (NS). There was a mean increase in heart rate of 10.8 ± 2.3 beats/min (P < 0.001) but no significant change in cardiac output. The calculated systemic vascular resistance fell by 10.0% ± 5.4% (P < 0.05). Associated with these changes there was a mean increase of 9.6% ± 1.5% (P < 0.05) in the counts from the calf. 5 Hydralazine caused a significant reduction in blood pressure and increase in heart rate. End-diastolic volume was reduced by 6.0% ± 2.7% but there was a mean increase in ejection fraction of 0.058 ± 0.010 (P < 0.001) so that in this instance stroke volume increased by 9.0% ± 3.7% (P < 0.05) and cardiac output increased by 16.4% ± 4.4% (P < 0.005). The calculated systemic vascular resistance fell by 18.9% ± 3.8% (P < 0.001). Despite these haemodynamic changes there was no significant change in counts from the calf. 6 The results confirm that GTN has a predominant venodilator effect while hydralazine acts largely on the arterial bed. These relatively simple radionuclide methods will allow a more detailed assessment of the cardiovascular effects of drugs.

Noninvasive radioisotope cardiographic images with digital prefiltering and boundary detection for measuring left ventricular parameters

Noninvasive radioisotope cardiographic techniques have become a useful tool in studying left ventricular anatomy and function. The data obtainable by these techniques are often corrupted by various noise sources, and the need for image quality improvement by selective digital filtering has become evident. This investigation describes a new sequential estimating algorithm useful for several different types of radioisotope cardiographic images. In particular, the sizing of acute myocardial infarcts using technetium-99 m stannous pyrophosphate ( 99 m Tc-PYP) scintigrams and the determination of left ventricular ejection fractions using the gated blood pool method are investigated before and after the sequential estimating algorithm was applied to the original images. The results demonstrate significant improvement in myocardial infarct sizing in animals after digital filtering as well as increased accuracy in left ventricular ejection fraction determinations when compared to cineangiocardiographic measurements. The findings suggest that these nontraumatic and relatively noninvasive techniques will have improved diagnostic capability when used in conjuction with digital filtering for serial evaluation and follow-up studies of both acutely ill and nonhospitalized patients.