Pulmonary thallium uptake: correlation with systolic and diastolic left ventricular function at rest and during exercise

Important parameters in the detection of left main trunk disease using stress myocardial perfusion imaging

OBJECTIVES

We sought noninvasively to diagnose left main trunk (LMT) disease using myocardial perfusion imaging (MPI).

METHODS

Five hundred and eight patients with suspected coronary artery disease (CAD) underwent both stress MPI and coronary angiography. The extent and severity of perfusion abnormalities were assessed using a 20-segment model. In addition, perfusion defects in both left anterior descending and left circumflex arterial territories were defined as a left main (LM) pattern defect, and those in 3-coronary arterial territories as a 3-vessel pattern defect.

RESULTS

In 42 patients with LMT disease, a summed stress score (19.4 ± 10.0 vs. 13.5 ± 10.0; p < 0.0001) and a summed rest score (12.1 ± 9.7 vs. 7.0 ± 7.8; p = 0.002) were greater than in 466 patients without LMT disease, while a summed difference score was similar (7.3 ± 7.7 vs. 6.5 ± 6.1; p = NS). The prevalence of an LM-pattern defect was low in both groups (12% vs. 8%; p = NS). However, a 3-vessel pattern defect (33% vs. 7%; p < 0.0001), lung uptake of radiotracers (38% vs. 11%; p < 0.0001), and transient ischemic dilation (31% vs. 13%; p = 0.003) were more frequently observed in patients with LMT disease than in those without. Logistic regression analysis showed that a 3-vessel pattern defect (OR=3.5, 95% CI = 1.4-8.8; p = 0.007), lung uptake of radiotracers (OR = 2.5, 95% CI = 1.1-5.7; p = 0.03), and previous myocardial infarction (MI) (OR = 2.4, 95% CI = 1.0-5.7; p = 0.05) were the most important parameters to detect LMT disease. After excluding 163 patients with previous MI, a repeat analysis revealed that lung uptake of radiotracers (OR = 8.2, 95% CI = 2.3-29.2; p = 0.001) and an LM-pattern defect (OR = 6.3, 95% CI = 1.4-27.2; p < 0.02) were independent predictors for LMT disease.

CONCLUSION

In the identification of LMT disease, lung uptake of radiotracers was a single best parameter, which was independent of the presence or absence of previous MI.

Increased resting Tl-201 lung-to-heart ratio is associated with invasively determined measures of left ventricular dysfunction, extent of coronary artery disease, and resting myocardial perfusion abnormalities

BACKGROUND

Stress lung thallium 201 uptake correlates with left ventricular (LV) dysfunction and extent of coronary artery disease (CAD). Although Tl-201 is used less commonly for stress imaging, dual-isotope stress and viability protocols continue to use Tl-201 for rest imaging. We sought to investigate the association between increased resting Tl-201 lung-to-heart ratio (LHR) and hemodynamic indices of LV dysfunction, indices of myocardial perfusion, and extent of CAD.

METHODS AND RESULTS

Over a 1-year period, we identified 192 consecutive patients who underwent dual-isotope stress perfusion imaging and cardiac catheterization within 30 days, without interim events or revascularization. Resting LHR was measured, and its association with invasively measured hemodynamic parameters, extent of CAD, and indices of myocardial perfusion at rest and stress was examined. Increased resting Tl-201 LHR was weakly but significantly associated with lower LV ejection fraction (EF) (r = 0.209, P <.05), higher pulmonary capillary wedge pressure (r = 0.25, P <.005), and LV end-diastolic pressure (r = 0.215, P <.01) but not with pulmonary artery systolic pressure. Increased LHR was also weakly associated with rest perfusion abnormalities including the sum rest score (r = 0.271, P <.001) and number of abnormally perfused segments (r = 0.25, P <.001) bud did not correlate with stress perfusion indices or ischemic burden. The 76 patients (40%) with LHR greater than 0.5 were more likely to have LVEF lower than 40% and 3-vessel/left main CAD.

CONCLUSIONS

Increased rest Tl-201 LHR is weakly associated with higher LV end-diastolic pressure and pulmonary capillary wedge pressure and lower LVEF. LHR is also associated with the extent of previously infarcted myocardium and may indicate the presence of 3-vessel/left main CAD.

Thallium-201 myocardial imaging at rest in male orienteers and other endurance athletes

During the period 1979 to 1992, 16 sudden unexpected cardiac deaths were known to have occurred in young Swedish orienteers. Autopsy indicated myocarditis to be the most frequent finding, most often combined with extensive myocardial fibrosis. The aim of the present investigation was to explore whether young male orienteers show a higher frequency than other young elite endurance athletes (controls) in the occurrence of Thallium-201 myocardial perfusion defects at rest, suggestive of fibrosis evoked by myocarditis. Thallium-201 perfusion abnormalities at rest were more frequently found in the controls than in the orienteers (26% vs. 12%, p=0.03). Uneven Tl-201 perfusion was associated with left ventricular mass (r=0.32, r=0.24, p<0.01, p=0.02) and body weight (r=0.30, r=0.31, p<0.01, p=0.03) in orienteers and controls, respectively. Echocardiographic left ventricular wall motion abnormalities were found in 11 athletes (9 orienteers and 2 controls) but only two displayed an abnormal Thallium-201 perfusion scan at rest. Perfusion abnormalities at rest did not occur more frequently in the orienteers but were commonly found in both groups of apparently healthy athletes making it futile to discern abnormals from normals. Thallium-201 perfusion aberrations were not associated with left ventricular wall motion abnormalities obtained by echocardiography.

Relation between aerobic capacity and extent of myocardial ischemia in patients with normal cardiac function

BACKGROUND

The relation between aerobic capacity and extent of exercise-induced myocardial ischemia has not been investigated. Fifty patients with coronary artery disease (>/=50% stenosis) without myocardial infarction underwent cardiopulmonary exercise testing followed by quantitative thallium perfusion imaging. Results were compared with those of age- and sex-matched healthy controls with a low likelihood of coronary artery disease. Patients with Q-wave infarction, pulmonary disease, and peripheral vascular disease were excluded. Cardiopulmonary exercise testing and thallium perfusion imaging parameters were correlated for extent of global ischemia, occurrence of increased pulmonary thallium uptake, and transient ventricular dilatation during exercise.

RESULTS

Patients with global ischemia <20% (group 1, n = 25) had normal cardiopulmonary exercise testing results, similar to the control group, except for workload and maximal predicted heart rate, which were reduced. However, patients with ischemia >/=20% (group 2, n = 25) had poor cardiopulmonary exercise testing results compared with the controls. The ventilatory anaerobic threshold showed the most significant decrease of all cardiopulmonary exercise testing parameters (48% +/- 6% vs 57% +/- 6%, P <.0001), and it was the only parameter to correlate with extent of ischemia (r = -0.5; P <.003) as well as frequency of increased pulmonary uptake and transient ventricular dilatation (r = -0.33, P =.03).

CONCLUSIONS

Ventilatory anaerobic threshold is significantly related to extent of myocardial ischemia and signs of heart failure during exercise. However, patients with mild to moderate exercise-induced ischemia may have normal cardiopulmonary exercise testing performance.

Comparison of pulmonary uptake with transient cavity dilation after exercise thallium-201 perfusion imaging

OBJECTIVES

The purpose of the study was to evaluate the relationship between elevated lung/heart ratio (LHR) and transient ischemic dilation (TID) after stress thallium-201 myocardial perfusion imaging and to provide further insight into the mechanism of cavity dilation.

BACKGROUND

Because both LHR and TID have been identified as adjunctive markers of severe coronary disease they should be found in the same patients. Although the mechanism of LHR has been defined, that of transient dilation has not.

METHODS

We identified 4,618 consecutive patients undergoing maximal exercise perfusion imaging with thallium-201. Lung/heart ratio and a dilation index were derived and compared to each other and to relevant clinical parameters.

RESULTS

There was a very weak relationship between the LHR and dilation index (r = 0.15, p < 0.001). Defining a dilation index > or =1.10 and LHR > or =50% as abnormal revealed that 322 of the patients (7%) had TID only, 351 (7.8%) had LHR only and 40 (0.9%) had both. When compared to patients without these findings both TID and LHR had higher thallium stress defect and redistribution scores. When comparing subjects who had elevated LHR uptake to those who had TID, it was found that those with LHR were more likely to have had prior myocardial infarction (MI) (29% vs. 9%), coronary artery bypass grafting (22% vs. 8%), lower ejection fraction (34+/-17% vs. 55+/-11%) and had more evidence of ischemia based on thallium stress defect and redistribution scores. However, patients with cavity dilation had a higher frequency of positive electrocardiographic response (31% vs. 19%) despite lower scintigraphic markers.

CONCLUSIONS

Although pulmonary uptake and transient cavity dilation have both been associated with severe coronary disease, they have a very weak correlation, which, in combination with the different clinical parameters associated with each, suggests that they represent different pathophysiologic responses to exercise-induced ischemia. Our data support the hypothesis that TID represents transient subendocardial ischemia rather than physical dilation from increased end-diastolic pressure.

Increased lung uptake during myocardial scintigraphy improves the detection and localization of coronary artery disease

Increased lung uptake during exercise thallium 201 scanning denotes severe ventricular hypofunction. To assess whether there is any relationship between this finding and the stenosis of a single coronary artery, the authors studied 140 patients (age 57.5 +/- 12 years) with both exercise thallium and coronary angiography within three months. A planar view was acquired for two hundred forty seconds immediately postexercise and prior to the single photon emission computed tomography acquisition. Two identical regions of interest outlining the left ventricle and the right lung in the planar view were used for calculation of the lung uptake, expressed as a lung-to-heart counts ratio. The patients were divided into four angiographic groups: (I) lesions at the left anterior descending (LAD), n = 35; (II) stenosis at the circumflex (CRX), n = 35; (III) stenosis at the right coronary artery (RCA), n = 35; and (IV) another group of 35 normal subjects serving as controls. No patient had a previous myocardial infraction (MI) or any cardiac operation. Patients in groups I (0.53 +/- 0.094) and II (0.44 +/- 0.072) had higher lung uptake than those in groups III (0.43 +/- 0.061) or IV (0.42 +/- 0.050). There was no difference between groups III and IV, or II and IV, but the difference between I and IV was of statistical significance (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Revascularization of infarcted myocardium. Effect on myocardial perfusion assessed with quantified Tl-201 SPECT technique

Myocardial perfusion was studied in 21 patients before and after revascularization of all graftable stenotic vessels following post-infarction anteroapical akinesia and minor dyskinesia. At preoperative and late postoperative evaluation, perfusion abnormalities in identified sectors were quantified with two methods, one (Q1) assessing the extent and the other (Q3) the severity of abnormal perfusion. The preoperative scores with both methods indicated permanent myocardial perfusion defects in all 21 patients and reversible defects, indicating myocardial ischemia, in 16 with Q1 and 14 with Q3. After bypass grafting there was overall reduction of myocardial perfusion defect and of abnormality scores: Notably, 13/21 patients (62%) had decreased permanent myocardial defect score, reflecting reactivation of 'hibernating myocardium'. The findings indicated that obstructed but graftable vessels supplying myocardium with loss of contractile function should be bypassed, since flow contribution to distant, viable myocardium is probable via preserved collateral circulation. This should be particularly relevant for the LAD, because of that artery's septal branches.