Serial evaluation of dilated cardiomyopathy with exercise thallium-201 tomography: correlation with the evolution of left ventricular parameters

Left ventricular wall motion abnormalities as well as reduced wall thickness can cause false positive results of routine SPECT perfusion imaging for detection of myocardial infarction

AIMS

The relationship between wall thickness, wall thickening, wall motion, and single-photon emission computed tomography (SPECT) results for detection of myocardial infarction has never been systematically evaluated in a clinical setting. In particular, the discussion whether non-ischaemic regional wall motion abnormalities and reduced wall thickness can cause SPECT to be false positive for infarct detection remains unsettled.

METHODS AND RESULTS

We therefore evaluated patients presenting with left bundle branch block (LBBB) and only included them in the analysis if any coronary artery disease (CAD) had been ruled out by angiography. LBBB is known to cause septal wall motion abnormalities as well as to reduce systolic septal wall thickness. Thus, LBBB is a good non-ischaemic clinical model to evaluate the influence of wall thickness and wall motion on the homogeneity of tracer distribution in resting SPECT images. SPECT revealed fixed defects in all 139 patients initially identified for possible enrollment. CAD was found to be present by angiography in 120 patients. The remaining 19 patients without any CAD underwent cardiovascular magnetic resonance (CMR) and were included in the study. Evaluation of SPECT using a 72-segment model revealed septum-related fixed defects in all 19 patients. Every defect was interpreted as myocardial infarction by blinded observers. The comparison of nuclear results to the gold standard CMR demonstrated that none of the fixed SPECT defects did represent myocardial infarcts. Defects, however, exactly matched areas of wall motion abnormalities as well as regions with impaired wall thickness as demonstrated by CMR. On a segmental basis, we found a strong relationship between wall motion and reduced wall thickness on one hand and SPECT defects on the other hand. For example, only 5% of segments with normal wall motion were false positive by SPECT for myocardial infarction, whereas 93% of all dyskinetic segments were found to be false positive (P<0.01). Comparing wall thickness to SPECT results revealed that 58% of segment in which wall thickness was 1 SD below the mean and 93% of segments in which wall thickness was 2 SD below the mean showed fixed defects by SPECT. Conversely, only 0.5% of segments in which wall thickness was above the mean were affected by false positive SPECT results (P<0.01).

CONCLUSION

Wall motion abnormalities as well as impaired myocardial wall thickening and wall thickness can cause false positive results of resting SPECT myocardial perfusion imaging for detection of myocardial infarction in the absence of myocardial infarct scars and CAD.

[123I]-phenylpentadecanoic acid uptake in patients with dilated cardiomyopathy

BACKGROUND

The rate constant for global fatty acid influx (k(1)) was studied in 12 male patients with dilated cardiomyopathy (DCM).

METHOD

10 normal subjects served as controls. 201-Thallium (201TI) and [123I]-phenyl-pentadecanoic acid (IPPA) were administered during bicycle exercise under fasting conditions.

RESULTS

All patients showed non-homogeneous tracer uptake defects for 201TI and IPPA. k(1) was significantly higher in DCM patients than controls. k(1) showed significant inverse correlation between cardiac index, left-ventricular ejection fraction, left-ventricular enddiastolic pressure and echocardiographic left-ventricular ejection fraction.

CONCLUSION

We presume that an increased regional rate constant of IPPA influx into the myocardial tissue in patients with DCM reflects a compensatory mechanism of altered myocardium.

Myocardial perfusion and function of the systemic right ventricle in patients after atrial switch procedure for complete transposition: long-term follow-up

OBJECTIVES

Our purpose was to assess the right ventricular (RV) function and identify patients with RV impairment long after the Mustard or Senning operation.

BACKGROUND

Systemic ventricular failure can cause myocardial perfusion abnormalities in thallium scintigraphy correlating with hemodynamic deterioration.

METHODS

Myocardial perfusion at rest and at peak exercise was assessed in 61 patients, aged 7 to 23 years in mean time 10.0 +/- 2.9 years after surgery using technetium-99m methoxyisobutyl isonitrile single-photon emission computed tomography. Ventricular function was assessed by first-pass radionuclide angiography at rest. Exercise capacity was determined with a modified Bruce protocol.

RESULTS

The mean RV ejection fraction was 36.1 +/- 7.7%, and left ventricular (LV) ejection fraction was 52.1 +/- 9.4%. Moderate or severe perfusion abnormalities on the rest scan were observed in 20 patients (33%). On exercise perfusion worsened in another 13 patients (21.3%). Patients with perfusion defects on stress scan had significantly lower RV and LV ejection fraction (33.2 vs. 39.4%; p = 0.002 and 49.2 vs. 55.5%; p = 0.01, respectively). They were also older (16.6 vs. 13.0 years; p = 0.002), operated on at an older age (4.0 vs. 2.4 years; p = 0.05) and had longer follow-up (12.5 vs. 10.5 years; p = 0.003).

CONCLUSIONS

Myocardial perfusion defects are common findings in patients in long-term follow-up after atrial switch operation. Despite excellent exercise tolerance, the extent of myocardial perfusion abnormalities correlated well with impaired RV and LV function, and greater perfusion defects were seen more frequently in older patients with longer follow-up. It is likely that myocardial perfusion defects could be a sensitive predictor of systemic ventricular impairment.