Impact of vascular adaptation to chronic aortic regurgitation on left ventricular performance.

BACKGROUND: This investigation was designed to test the hypothesis that vascular adaptation occurs in patients with chronic aortic regurgitation to maintain left ventricular (LV) performance. METHODS AND RESULTS: Forty-five patients with chronic aortic regurgitation (mean age 50+/-14 years) were studied using a micromanometer LV catheter to obtain LV pressures and radionuclide ventriculography to obtain LV volumes during multiple loading conditions and right atrial pacing. These 45 patients were subgrouped according to their LV contractility (Ees) and ejection fraction values. Group I consisted of 24 patients with a normal Ees. Group IIa consisted of 10 patients with impaired Ees values (Ees <1.00 mm Hg/mL) but normal LV ejection fractions; Group IIb consisted of 11 patients with impaired contractility and reduced LV ejection fractions. The left ventricular-arterial coupling ratio, Ees/Ea, where Ea was calculated by dividing the LV end-systolic pressure by LV stroke volume, averaged 1.60+/-0.91 in Group I. It decreased to 0.91+/-0.27 in Group IIa (P<0.05 versus Group I), and it decreased further in Group IIb to 0.43+/-0.24 (P<0.001 versus Groups I and IIa). The LV ejection fractions were inversely related to the Ea values in both the normal and impaired contractility groups (r=-0.48, P<0.05 and r=-0.56, P<0.01, respectively), although the slopes of these relationships differed (P<0.05). The average LV work was maximal in Group IIa when the left ventricular-arterial coupling ratio was near 1.0 because of a significant decrease in total arterial elastance (P<0.01 versus Group I). In contrast, the decrease in the left ventricular-arterial coupling ratio in Group IIb was caused by an increase in total arterial elastance, effectively double loading the LV, contributing to a decrease in LV pump efficiency (P<0.01 versus Group IIa and P<0.001 versus Group I). CONCLUSIONS: Vascular adaptation may be heterogeneous in patients with chronic aortic regurgitation. In some, total arterial elastance decreases to maximize LV work and maintain LV performance, whereas in others, it increases, thereby double loading the LV, contributing to afterload excess and a deterioration in LV performance that is most prominent in those with impaired contractility.

Effects of beta-adrenergic blocking therapy on left ventricular diastolic relaxation properties in patients with dilated cardiomyopathy.

BACKGROUND: The hemodynamic mechanism for the improvement in left ventricle (LV) end-diastolic pressure in cardiomyopathy patients treated with beta-adrenergic blocking agents is controversial. We hypothesized that the salutary effect of this kind of therapy on LV end-diastolic pressure would be indicative of an improvement in late, passive diastolic relaxation properties. METHODS AND RESULTS: We studied 14 cardiomyopathy patients in normal sinus rhythm with no arteriographic evidence of coronary artery disease and an LV ejection fraction of

Impaired left ventricular contractile function in patients with long-term mitral regurgitation and normal ejection fraction.

OBJECTIVES: We tested the hypotheses that left ventricular chamber elastance would detect impaired contractile function in patients with long-term mitral regurgitation and a normal ejection fraction and that these patients would have unique temporal left ventricular size and ejection fraction responses to mitral valve surgery. BACKGROUND: Although it has been suggested that left ventricular contractile function may begin deteriorating in patients with long-term mitral regurgitation whereas ejection fraction remains normal, no data exist in humans. METHODS: We studied 11 control patients and 28 patients with long-term mitral regurgitation using micromanometer-measured pressures, biplane contrast cineventriculography and radionuclide angiography under control conditions and with alterations in load during right atrial pacing to calculate left ventricular chamber elastance and myocardial stiffness. RESULTS: The patients with mitral regurgitation were classified into subgroups: Group I, normal contractile function; Group II, impaired contractile function (reduced Emax) but normal ejection fraction, and Group III, impaired contractile function (reduced Emax) with reduced systolic myocardial stiffness. Twenty-two of the patients with mitral regurgitation underwent mitral valve surgery. In Group I, comparable decreases in left ventricular volume indexes (p < 0.01 and p = 0.05, respectively) were associated with no change in ejection fraction at 3 months and 1 year. In contrast, in Group II, reductions in volume indexes (p < 0.0001 and p < 0.001) were associated with a short-term decrease in ejection fraction (p < 0.001) that recovered at 1 year (p < 0.01 vs. short-term). Finally, in Group III, variable responses in volume indexes were associated with a consistent decrease in ejection fraction at 3 months and 1 year. CONCLUSIONS: An analysis of left ventricular chamber elastance provides data to support the concepts that 1) contractile function is impaired in some patients with long-term mitral regurgitation and a normal ejection fraction, 2) impaired contractile function may not be irreversible in all of these patients, and 3) an earlier consideration of mitral valve surgery may be warranted to preserve contractile function in these patients.

Load dependence of the single beat maximal pressure (stress)/volume ratios in humans.

To determine whether the slopes of the single beat maximal pressure (stress)/volume ratios are sensitive to changes in loading conditions in humans, 16 patients without cardiac disease were studied with simultaneous micromanometer-determined left ventricular pressures and biplane contrast cineangiograms under control conditions and during methoxamine and nitroprusside infusions. Left ventricular volumes were calculated with use of a Simpson's rule algorithm, wall thickness was obtained iteratively, and both midwall circumferential and meridional stresses were computed frame by frame. The maximal pressure/volume and both circumferential and meridional maximal stress/volume ratios were calculated using a single beat from each loading condition assuming a zero volume-axis intercept. Mean left ventricular systolic pressure increased 47% during the methoxamine infusion and decreased 22% during the nitroprusside infusion compared with control (p less than 0.001 for both). Despite these changes in left ventricular systolic pressure, heart rate was eliminated as a confounding variable by right atrial pacing; and mean maximal rate of change of left ventricular pressure [(+)dP/dtmax] and rate of change at developed pressure 40 mm Hg [(+)(dP/dt) per DP40] values did not differ significantly. Mean single beat maximal pressure/volume ratios also did not differ significantly among the three loading conditions. In contrast, mean single beat circumferential and meridional maximal stress/volume ratios were 3.15 +/- 1.83 and 1.40 +/- 0.82 g/cm2 per ml at control; they increased to 4.47 +/- 2.44 and 2.21 +/- 1.25 g/cm2 per ml during the methoxamine infusion (p less than 0.001 for both), and they decreased during the nitroprusside infusion to 2.58 +/- 1.47 and 1.14 +/- 0.57 g/cm2 per ml (p less than 0.05 and p less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms for left ventricular systolic dysfunction in aortic regurgitation: importance for predicting the functional response to aortic valve replacement.

To test the hypothesis that the combined use of the time-varying elastance concept and conventional circumferential stress-shortening relations would elucidate differential mechanisms for left ventricular systolic dysfunction in severe, chronic aortic regurgitation and therefore predict the functional responses to aortic valve replacement, 31 control patients and 37 patients with aortic regurgitation were studied. The studies included micromanometer left ventricular pressure determinations, biplane contrast cineangiograms under control conditions and radionuclide angiograms under control conditions and during methoxamine or nitroprusside infusions with right atrial pacing. The patients with aortic regurgitation were classified into three groups: Group I had normal Emax and stress-shortening relations, Group II had abnormal Emax but normal stress-shortening relations and Group III had abnormal Emax and stress-shortening relations. The left ventricular end-diastolic and end-systolic volumes showed a progressive increase and the ejection fraction showed a progressive decrease from Group I to III; these values differed from those in the control patients (p less than 0.001). In Group I, there was a decrease in left ventricular volumes (p less than 0.05) but no significant change in ejection fraction (61 +/- 7% versus 63 +/- 4%) after aortic valve replacement. In contrast, in Group II, reduction in left ventricular volumes (p less than 0.01) was associated with an increase in ejection fraction from 50 +/- 8% to 64 +/- 11% (p less than 0.01). Finally, in Group III, reduction in left ventricular volumes (p less than 0.05) was associated with a further decrement in ejection fraction from 35 +/- 13% to 30 +/- 13%. Group I patients had compensated adequately for chronic volume overload. However, Group II had left ventricular dysfunction that was associated with an increase in the left ventricular volume/mass ratio compared with that in the control patients and Group I (p less than 0.05 for both), suggesting inadequate hypertrophy and assumption of spherical geometry. Finally, irreversible myocardial dysfunction had supervened in Group III. In conclusion, a combined analysis of left ventricular chamber performance using the time-varying elastance concept and myocardial performance using conventional circumferential stress-shortening relations provides complementary information that elucidates differential mechanisms for left ventricular systolic dysfunction and therefore predicts the functional response to aortic valve replacement.

First transit and equilibrium radionuclide angiography in patients with inferior transmural myocardial infarction: criteria for the diagnosis of associated hemodynamically significant right ventricular infarction.

To define radionuclide criteria for identifying hemodynamically significant right ventricular infarction, 33 consecutive men with inferior transmural infarction were evaluated prospectively by right heart catheterization and first transit and equilibrium radionuclide angiography within 36 hours of the onset of symptoms. Hemodynamically significant right ventricular infarction was present in 6 of the 33 patients (Group I); the remaining 27 patients did not demonstrate the hemodynamics characteristic of right ventricular infarction (Group II). A right ventricular ejection fraction of less than 40% separated Group I and Group II patients by equilibrium (p = 0.003) but not by first transit (p = NS) radionuclide angiography. However, a right ventricular ejection fraction of less than 35% separated Group I and II patients by both techniques (p = 0.02 and p = 0.005, respectively). The presence of a right ventricular regional wall motion abnormality on either first transit or equilibrium radionuclide angiograms separated Group I and II patients (p less than 0.001). The combination of both a right ventricular ejection fraction of less than 40% and a regional wall motion abnormality separated Group I and II patients using either equilibrium (p less than 0.001) or first transit (p = 0.02) radionuclide angiography. It is concluded that in patients with acute inferior transmural myocardial infarction, a right ventricular regional wall motion abnormality alone or in combination with a right ventricular ejection fraction of less than 40% by either first transit or equilibrium radionuclide angiography is a useful criterion for establishing the presence of hemodynamically significant right ventricular infarction, while its absence argues against the diagnosis of right ventricular infarction.

Beneficial hemodynamic effects of intravenous and oral diltiazem in severe congestive heart failure.

Concern persists about the potential negative inotropic effects of calcium channel blockers in patients with severely depressed myocardial function. Therefore, intravenous diltiazem (100 to 200 micrograms/kg per min infusion) was administered for 40 minutes followed by oral diltiazem (90 to 120 mg/8 hours) for 24 hours to patients with advanced congestive heart failure (New York Heart Association class III to IV, mean ejection fraction 26 +/- 4 [SD]). Intravenous diltiazem (eight patients) increased cardiac index 20% (2.05 +/- 0.8 to 2.47 +/- 0.8 liters/min per m2, p less than 0.01), stroke volume index 50% (22 +/- 9 to 33 +/- 12 ml/m2, p less than 0.001) and stroke work index 27% (19 +/- 10 to 24 +/- 10 g-m/m2, p less than 0.05); while reducing heart rate 23% (97 +/- 18 to 75 +/- 11 beats/min, p less than 0.01), mean arterial pressure 18% (95 +/- 13 to 78 +/- 7 mm Hg) and pulmonary wedge pressure 34% (29 +/- 9 to 19 +/- 7 mm Hg), without altering maximal first derivative of left ventricular pressure (dP/dtmax). Oral diltiazem (seven patients) produced equivalent hemodynamic effects. Transient junctional arrhythmias were observed in three of eight patients with intravenous diltiazem and one of seven patients with oral diltiazem. It is concluded that intravenous and short-term oral diltiazem improve left ventricular performance and reduce myocardial oxygen demand by heart rate and afterload reduction without significantly depressing contractile function in severe congestive heart failure. Caution should be exercised to avoid potential adverse, drug-induced electrophysiologic effects in such patients.

Value of noninvasive techniques for predicting early complications in patients with clinical class II acute myocardial infarction.

Twenty-six consecutive patients with acute clinical class II myocardial infarction were prospectively evaluated to assess the ability of two-dimensional echocardiography and gated equilibrium radionuclide angiography to predict early morbidity and mortality. Within 48 hours of the onset of symptoms, right heart catheterization, two-dimensional echocardiography and radionuclide angiography were performed. Serious in-hospital complications developed in 7 patients (27%, Group I), while the remaining 19 patients (Group II) had no complications. Mean left ventricular stroke work index was the only hemodynamic variable that differed significantly between Group I and Group II (28 +/- 8 [standard deviation] vs. 39 +/- 13 g-m/m2, respectively, p less than 0.02). Also, Group I compared with Group II had a significantly lower mean left ventricular ejection fraction by two-dimensional echocardiography (26 +/- 5 vs. 51 +/- 10%, p less than 0.001) or by radionuclide angiography (29 +/- 9 vs. 46 +/- 12%, p less than 0.001). Similarly, Group I had a higher average wall motion index than Group II by both techniques (2.2 +/- 0.2 vs. 1.7 +/- 0.3, p less than 0.001 by two-dimensional echocardiography, and 2.1 +/- 0.3 vs. 1.7 +/- 0.3, p less than 0.001 by radionuclide angiography). Selected stepwise multiple regression analysis demonstrated that left ventricular ejection fraction or wall motion index, by two-dimensional echocardiography or radionuclide angiography, had additional value to a history of prior myocardial infarction for predicting in-hospital complications in patients with class II infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Arbutamine stress thallium-201 single-photon emission computed tomography using a computerized closed-loop delivery system. Multicenter trial for evaluation of safety and diagnostic accuracy. The International Arbutamine Study Group.

OBJECTIVES: This study sought to evaluate the efficacy and safety of arbutamine when used in conjunction with thallium-201 single-photon emission computed tomography (SPECT) in a multicenter trial and to compare arbutamine stress and treadmill exercise thallium-201 SPECT for diagnostic sensitivity and myocardial perfusion pattern. BACKGROUND: Arbutamine is a potent beta-agonist developed specifically for pharmacologic stress testing. METHODS: Arbutamine was administered by a novel computerized closed-loop device that measures heart rate and adjusts arbutamine infusion to achieve a selected rate of heart rate increase toward a predetermined limit. The cohort included 184 patients who underwent arbutamine stress testing, of whom 122 (catheterization group) had angiographically defined coronary artery disease ( > or = 50% diameter stenosis of a major coronary artery), and 62 had a low pretest likelihood of coronary artery disease (low likelihood group). A subset of 69 patients from the catheterization group underwent both arbutamine and exercise stress testing. RESULTS: Hemodynamic responses during arbutamine and exercise stress testing demonstrated no significant difference in percent increase in heart rate (81% vs. 76%) or systolic blood pressure (26% vs. 30%). The sensitivity for detecting coronary artery disease ( > or = 50% stenosis) using arbutamine thallium-201 SPECT was 87% (95% for detecting > or = 70% stenoses), and the normalcy rate in the low likelihood group was 90%. In patients completing both arbutamine and exercise stress testing, thallium-201 SPECT sensitivity for detecting coronary artery disease ( > or = 50% stenosis) was 94% and 97% (p = NS), respectively Furthermore, SPECT segmental visual score agreement (defect vs. no defect) showed a concordance of 92% between arbutamine and exercise results (kappa 0.80, p < 0.001). The stress thallium-201 SPECT segmental scores showed 83% exact agreement (kappa 0.69, p < 0.001), and analysis of the reversibility of segments with stress perfusion defects demonstrated 86% exact agreement (kappa 0.68, p < 0.001). In general, side effects associated with arbutamine were well tolerated and resolved with discontinuation of infusion. CONCLUSIONS: Arbutamine, administered by a closed-loop feed-back system was shown to be a safe and effective pharmacologic stress agent. Arbutamine stress thallium-201 SPECT appears to be accurate for the diagnosis of coronary artery disease with a diagnostic efficacy similar to that of treadmill exercise thallium-201 studies.

Accurate estimates of absolute left ventricular volumes from equilibrium radionuclide angiographic count data using a simple geometric attenuation correction.

To simplify and clarify the methods of obtaining attenuation-corrected equilibrium radionuclide angiographic estimates of absolute left ventricular volumes, 27 patients who also had biplane contrast cineangiography were evaluated. Background-corrected left ventricular end-diastolic and end-systolic counts were obtained by semiautomated variable and hand-drawn regions of interest and were normalized to cardiac cycles processed, frame rate and blood sample counts. Blood sample counts were acquired on (d degree) and at a distance (d') from the collimator. A simple geometric attenuation correction was performed to obtain absolute left ventricular volume estimates. Using blood sample counts obtained at d degree or d', the attentuation-corrected radionuclide left ventricular end-diastolic volume estimates using both region of interest selection methods correlated with the cineangiographic end-diastolic volumes (r = 0.95 to 0.96). However, both mean radionuclide semiautomated variable left ventricular end-diastolic volumes (179 +/- 100 [+/- 1 standard deviation] and 185 +/- 102 ml, p less than 0.001) were smaller than the average cineangiographic end-diastolic volume (217 +/- 102 ml), and both mean hand-drawn left ventricular end-diastolic volumes (212 +/- 104 and 220 +/- 106 ml) did not differ from the average cineangiographic end-diastolic volume. Using the blood sample counts obtained at d degree or d', the attenuation-corrected radionuclide left ventricular end-systolic volume estimates using both region of interest selection methods correlated with the cineangiographic end-systolic volumes (r = 0.96 to 0.98). Also, using blood sample counts at d degree, the mean radionuclide semiautomated variable left ventricular end-systolic volume (116 +/- 98 ml, p less than 0.05) was less than the average cineangiographic end-systolic volume (128 +/- 98 ml), and the other radionuclide end-systolic volumes did not differ from the average cineangiographic end-systolic volume. Therefore, it is concluded that: 1) a simple geometric attenuation-correction of radionuclide left ventricular end-diastolic and end-systolic count data provides accurate estimates of biplane cineangiographic end-diastolic and end-systolic volumes; and 2) the hand-drawn region of interest selection method, unlike the semiautomated variable method that underestimates end-diastolic and end-systolic volumes, provides more accurate estimates of biplane cineangiographic left ventricular volumes irrespective of the distance blood sample counts are acquired from the collimator.

Right ventricular infarction: identification by hemodynamic measurements before and after volume loading and correlation with noninvasive techniques.

To evaluate the potential occurrence of right ventricular infarction, 53 patients with acute inferior transmural myocardial infarction were studied within 36 hours of symptoms by right heart catheterization, equilibrium radionuclide angiography and two-dimensional echocardiography. Technetium-99m pyrophosphate myocardial scintigraphy was performed 3 days after the onset of symptoms. The hemodynamic standard for right ventricular infarction was defined as both a right atrial pressure of 10 mm Hg or more and a right atrial/pulmonary artery wedge pressure ratio of 0.8 or more. Eight (15%) of the 53 patients had hemodynamic measurements at rest characteristic of right ventricular infarction, and 6 (11%) additional patients met these criteria after volume loading (p less than 0.05). Nineteen (37%) of the 51 patients who had radionuclide angiography had right ventricular dysfunction manifested by both a reduced right ventricular ejection fraction (less than 40%) and right ventricular regional wall motion abnormalities (akinesia or dyskinesia). An abnormal radionuclide angiogram was observed in 12 of 13 patients with hemodynamic measurements indicating right ventricular infarction. In 12 patients with an abnormal radionuclide angiographic study, right ventricular ejection fraction improved 6 to 12 weeks after infarction (27 +/- 7 to 36 +/- 9%, p less than 0.01). Twenty-two (49%) of the 45 patients with adequate two-dimensional echocardiograms had a right ventricular regional wall motion abnormality. An abnormal two-dimensional echocardiogram was seen in 9 of 11 patients with hemodynamic measurements characteristic of right ventricular infarction. Technetium-99m pyrophosphate scintigraphy was positive for right ventricular infarction in 3 of 12 patients who had hemodynamic measurements indicating right ventricular infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress testing with closed-loop arbutamine as an alternative to exercise. The International Arbutamine Study Group.

OBJECTIVES: This study compared exercise and pharmacologic stress testing using arbutamine delivered by a closed-loop device for the detection of coronary artery disease. BACKGROUND: Arbutamine, an agent designed to simulate exercise, has been developed in conjunction with a closed-loop delivery device that modulates the rate of administration on the basis of physiologic feedback. METHODS: Two hundred ten patients (180 men, 30 women) with symptoms and angiographic evidence of coronary artery disease were studied. Ischemia was categorized in three ways: 1) the presence of angina; 2) the occurrence of > or = 0.1-mV horizontal or downsloping ST segment depression or elevation at 60 ms after the J point; or 3) the presence of either condition 1 or 2. RESULTS: In the 210 patients, the mean increase in heart rate and systolic blood pressure evoked by arbutamine and exercise was 51 and 53 beats/min (p = NS) and 36 and 44 mm Hg (p < 0.0001), respectively. Arbutamine detected ischemia more often than exercise with each of the three ischemic end points. Sensitivity for detecting ischemia by either angina or ST segment change was 84% (95% confidence interval ¿ change was 84% (95% confidence interval [CI] 79% to 89%) for arbutamine and 75% (95% CI 69% to 81%) for exercise testing (p = 0.014). For angina alone, sensitivity was 73% (95% CI 67% to 79%) for arbutamine and 64% (95% CI 57% to 71%) for exercise (p = 0.026). For ST segment change alone, sensitivity was 47% (95% CI 40% to 54%) for arbutamine and 44% (95% CI 37% to 51%) for exercise (p = 0.426). Cardiac events occurred in five patients (1.8%) within 24 h of the arbutamine test. CONCLUSIONS: In detecting documented coronary artery disease, the sensitivity of arbutamine testing was equal to that of exercise for the electrocardiographic end point of ST segment change alone. Arbutamine testing was significantly superior to exercise testing for either ST change or angina or for angina alone.

Arbutamine echocardiography: efficacy and safety of a new pharmacologic stress agent to induce myocardial ischemia and detect coronary artery disease. The International Arbutamine Study Group.

OBJECTIVES: This study sought to determine the efficacy and safety of arbutamine echocardiography in inducing myocardial ischemia and detecting coronary artery disease. BACKGROUND: Exercise and pharmacologic stress echocardiography are clinically accepted techniques for detecting coronary artery disease. Arbutamine is a new synthetic beta-adrenoceptor agonist developed specifically as a stress agent. Arbutamine is delivered by a new computerized drug delivery device that adjusts the rate of drug infusion according to the patient's heart rate response during stress testing. METHODS: The sensitivity of arbutamine echocardiography was determined in 143 patients who had coronary artery disease documented by coronary angiography. A subset of these patients (n = 114) also underwent exercise echocardiography. The specificity, or normalcy, of arbutamine echocardiography was determined in 54 patients considered to have a low likelihood of coronary artery disease. RESULTS: Among those patients who had both stress test results, the incidence of inducing myocardial ischemia (new or worsening wall motion abnormalities) was 79% (95% confidence interval [CI] 69% to 86%, n = 98) for arbutamine and 77% (95% CI 67% to 85%, n = 98) for exercise echocardiography. The sensitivity of detecting coronary artery disease (ischemia or rest wall motion abnormality) was 87% (95% CI 79% to 93%, n = 101) for arbutamine and 83% (95% CI 74% to 90%, n = 101) for exercise echocardiography. The specificity (normalcy) of arbutamine echocardiogrpahy was 96% (95% CI 87% to 100%, n = 52). Arbutamine was well tolerated, and there were no serious adverse events. CONCLUSIONS: Arbutamine echocardiography is an effective and safe pharmacologic stress test technique for diagnosing or excluding the presence of coronary artery disease. The ability of arbutamine stress to induce myocardial ischemia, detectable by echocardiography, was comparable to that for exercise.

Quantification of left-ventricular regional dyssynergy by radionuclide angiography.

To determine whether variables obtained from Fourier analysis of gated equilibrium radionuclide angiographic (RNA) images can detect and quantify changes in left-ventricular (LV) regional wall motion induced by transient ischemia, 11 chronically instrumented dogs were simultaneously studied with hemodynamic measurements and RNA during control, left circumflex (LCx) coronary artery occlusion, and postocclusion conditions. The dogs were preinstrumented with aortic and LV catheters, electromagnetic aortic and LCx coronary artery flow probes, high-fidelity LV micromanometers, LCx coronary artery occluders, and 4-mm ultrasonic transverse LV diameter and 2-mm regional LV segment crystal pairs. Radionuclide LV regional phase and amplitude variables were calculated for each condition. The absolute changes in LCx region RNA mean, median, and standard deviation of mean phase correlated with the percent changes in LCx segment crystal fractional shortening (r = -0.71, -0.64, and -0.51, respectively; all p less than or equal to 0.01). Similarly, the absolute changes and percent changes in LCx region RNA mean amplitude per pixel correlated with the percent changes in LCx segment crystal fractional shortening (r = 0.89 and 0.94, respectively; both p less than 0.001). When these LCx region RNA phase variables were subgrouped according to mild or severe depression or augmentation in LCx segment crystal fractional shortening, progressive differences were observed between the average values for these subgroups (p less than 0.05 to p less than 0.001). These data, therefore, suggest that these regional RNA phase variables may be able to detect and quantify alterations in LV contraction patterns due to transient ischemia.

Noninvasive quantitation of right-ventricular volume overload in adults by gated equilibrium radionuclide angiography.

R-wave-synchronized equilibrium radionuclide angiography (RNA) is a noninvasive method whose time-activity curves provide count information that is proportional to ventricular volume. We have performed resting gated RNA in nine consecutive adult patients undergoing cardiac catheterization for evaluation of left-to-right shunting. Pulmonary/systemic flow ratios (Qp/Qs) calculated from RNA correlated well with Qp/Qs defined by oximetry (r = 0.87, y = 0.85x + 0.11, sy . x = 0.46). In five patients imaged before, and within 1 mo after, successful surgical repair, RNA Qp/Qs declined from a mean (+/- s.d.) of 2.9 +/- 1.0 to 1.1 +/- 0.2. Right/left ventricular end-diastolic volume ratios declined from 3.1 +/- 1.3 to 1.7 +/- 0.2. Although left-ventricular ejection fraction did not change, right-ventricular ejection fraction declined in these patients. Imaging in nine patients with right-ventricular dysfunction, but without shunt or regurgitation, yielded a mean Qp/Qs of 0.94 +/- 0.27. We conclude that Qp/Qs, right-ventricular ejection fraction, and relative ventricular enlargement may be accurately quantitated and followed serially after therapeutic intervention using gated RNA.

Effect of errors in reangulation on planar and tomographic thallium-201 washout profile curves.

Cardiac phantom studies were performed with and without a defect present to test the hypothesis that myocardial 201TI quantitative circumferential washout profile curves calculated from planar and rotating slant hole (RSH) collimator tomographic images are equally affected by errors in axial repositioning. Simulated stress images were acquired with the long axis of the phantom perpendicular to the camera surface and redistribution images were acquired to represent 50% 201TI washout with axial repositioning errors relative to the stress position ranging from 0 to 20 degrees in 5 degrees increments. There was a decrease in the 201TI washout profile curves compared to that expected (50%) in the wall tilted away from the camera surface, and a reciprocal increase in the 201TI washout profile curves in the wall tilted towards the camera surface for both imaging techniques whether a lesion was present or not. This effect became more pronounced as the error in axial repositioning was increased for both the planar (p less than 0.001) and the RSH tomographic (p less than 0.001) techniques. However, the deviation of the 201TI washout profile curves from that expected (50%) was greater for the planar imaging technique with or without a lesion (p less than 0.05 to 0.001). Thus, we conclude that 201TI quantitative circumferential washout profile curves calculated using this tomographic imaging technique are less affected by errors in axial repositioning than those calculated using an equivalent projection by standard planar imaging methods. These data emphasize the importance which must be placed on the repositioning of patients to obtain valid 201TI washout profile curves for the detection and localization of coronary artery disease.

Effects of alterations in systolic pressure on radionuclide measurements of left ventricular filling dynamics.

To determine the effects of steady-state left ventricular systolic pressure alterations on radionuclide measures of left ventricular filling dynamics, we studied 15 normal patients and 17 patients with nonischemic heart disease. Micromanometer left ventricular pressures and computer assisted forward gated radionuclide angiograms were acquired simultaneously. Right atrial pacing maintained heart rates constant during the baseline condition and methoxamine and nitroprusside infusions. Diastolic filling dynamics, peak filling rate and time to peak filling rate were calculated using a three harmonic Fourier analysis of the left ventricular time-activity curves. Left ventricular systolic pressure increased to 165 +/- 25 mmHg with methoxamine (p < 0.001) and decreased to 106 +/- 18 mmHg with nitroprusside (p < 0.001) from a baseline value of 133 +/- 16 mmHg. Radionuclide left ventricular filling dynamics did not change significantly. Thus, we conclude that radionuclide measurements of left ventricular filling dynamics are not affected by modest, steady-state alterations in left ventricular systolic pressure and can therefore be useful for the assessment of left ventricular diastolic function during interventions which may also affect left ventricular systolic pressure.

First-pass anger camera radiocardiography: biventricular ejection fraction, flow, and volume measurements.

First-pass (FP) right and left ventricular ejection fraction results were compared with equilibrium radiocardiographic (ER) measurements, and FP left ventricular ejection fraction (LVEF) values were compared with biplane contrast angiographic (CA) measurements in 13 patients with and seven patients without regurgitant valvular disease. Regurgitant fractions were calculated from differences between the FP right and left ventricular stroke volumes. Ejection fractions determined by FP were precise (mean CV = 9.6% RVEF, 13.4% LVEF). Mean LVEF by FP and ER were essentially identical, and both were lower than by CA. LVEF(FP) correlated with LVEF by ER and CA (r = 0.88, p less than 0.001). Mean RVEF by both FP and ER were also correlated (r = 0.82, p less than 0.001). There was correlation between FP (corrected) and CA left ventricular stroke (r = 0.77), end-diastolic (r = 0.88), and end-systolic (r = 0.91) volumes, but underestimates were noted when uncorrected flows were used (r = 0.52-0.71). The FP regurgitant fraction measurements separated the patients with regurgitant valvular disease from those without and agreed well with CA grading of regurgitation.

Assessment of the radionuclide angiographic left ventricular maximum time-varying elastance calculation in man.

This investigation was designed to determine whether left ventricular (LV) maximum time-varying elastance (Emax) calculations obtained using equilibrium radionuclide angiography (RNA) were comparable to those obtained using biplane contrast cineangiography (CINE), and whether simple, indirect P-V relations might provide reasonable, alternative estimates of Emax. Accordingly, we studied 19 patients with simultaneous high-fidelity micromanometer LV and fluid brachial artery (Ba) pressure recordings, CINE, and RNA under control conditions and during methoxamine and nitroprusside infusions. Emax was defined for CINE and RNA as the maximum slope of the linear relation of isochronal, instantaneous P-V data points obtained from each of the three loading conditions. The indirect P-V relations were similarly obtained from Ba peak (P) pressure versus minimum RNA LV volume (BaP/minV) and Ba dicrotic notch (di) pressure versus minimum RNA LV volume (Badi/minV) data points. The mean heart rates and LV (+)dP/dtmax values were minimally altered during the three loading conditions. The isochronal Emax values ranged from 1.40 to 6.73 mmHg/ml (mean 4.13 +/- 1.99 s.d. mmHg/ml) for CINE and from 1.48 to 7.25 (mean 4.35 +/- 1.81 mmHg/ml) for RNA (p = N.S.). Similarly, the unstressed volumes ranged from -10 to 80 ml (mean 30 +/- 23 ml) for CINE and from -8 to 77 ml (29 +/- 21 ml) for RNA (p = N.S.). The individual, isochronal Emax values by RNA correlated with those by CINE (r = 0.86). In 14 of the 19 patients, the BaP/minV and Badi/minV relations correlated with the isochronal Emax values calculated by RNA (r = 0.83 and 0.82, respectively), and these relations also correlated with the Emax values calculated by CINE (r = 0.82 and 0.78, respectively). The slope and V0 values for the BaP/minV and Badi/minV relations underestimated those for Emax by RNA and CINE (p less than 0.01 and p less than 0.05, respectively, for both). Thus, the isochronal Emax values calculated using RNA are comparable to those obtained using CINE in man. Moreover, indirect P-V relations underestimate these Emax values, but they are linearly related with the isochronal Emax values calculated by RNA and CINE. Consequently, these indirect P-V relations may provide a more simple, alternative estimate of LV contractile function in man.

Estimates of left-ventricular volumes by equilibrium radionuclide angiography: importance of attenuation correction.

To compare the accuracy of attenuated and attenuation-corrected equilibrium radionuclide angiographic (RNA) left ventricular (LV) volume estimates, we studied 23 consecutive patients with biplane contrast cineangiography (CINE). Attenuated RNA end-diastolic (ED) and end-systolic (ES) volumes were calculated from background-corrected ED and ES counts obtained from hand-drawn regions of interest that were normalized to cardiac cycles processed, frame rate, and blood activity. A simple, geometric attenuation correction was performed to obtain attenuation-corrected RNA LV volumes. The attenuated and attenuation-corrected RNA LV EDV estimates correlated with the CINE LV EDVs ; however, the attenuation-corrected RNA LV EDV estimates correlated more closely. Also, the average attenuation-corrected RNA LV EDV did not differ significantly from the mean CINE LV EDV. Attenuated and attenuation-corrected RNA LV ESV estimates also correlated with the CINE LV ESVs , but the attenuation-corrected RNA LV ESV estimates correlated more closely. Also, the average attenuation-corrected RNA LV ESV did not differ significantly from the mean biplane CINE LV ESV.