Usefulness of chronotropic incompetence to dipyridamole in predicting myocardial perfusion defects in heart transplant recipients

Chronotropic response to vasodilator-stress in patients submitted to myocardial perfusion imaging: impact on the accuracy in detecting coronary stenosis

AIMS

A lower heart rate response (HRR) during vasodilator MPI has been shown to have a relevant adverse prognostic impact. We sought to evaluate the interaction among individual HRR to vasodilator stress and myocardial perfusion imaging (MPI) accuracy in patients with suspected ischemic heart disease (IHD).

METHODS AND RESULTS

One hundred and sixty-five consecutive patients were submitted to vasodilator-stress MPI on a cardiac camera equipped with cadmium-zinc-thelluride detectors and coronary angiography. A coronary stenosis >70 % was considered significant. In every patient, the summed difference score (SDS) was computed from MPI images. Patients were categorized according to the tertiles of the distribution of individual HRR during dipyridamole: "Group 1" (HRR < 8 bpm; lowest tertile); "Group 2" (8 ≤ HRR ≤ 12 bpm; middle tertile); "Group 3" (HRR >12 bpm; highest tertile). Significant coronary artery disease (CAD) was present in 102 (62 %) patients. In the overall population, MPI showed a significant accuracy (AUC: 0.81, 95 % CI 0.74-0.86; p < 0.001) in unmasking the presence of significant coronary stenosis. Interestingly, in patients with a blunted HRR during dipyridamole ("Group 1") MPI showed a significantly lower sensitivity (68 %) in detecting CAD than in those with a higher HRR ("Group 3") (91 %, p = 0.007), despite a preserved specificity (76 % vs 77 %, P=NS). Similarly, the correlation among CAD extent and post-stress LV functional stunning was limited to "Group 3" patients, while it disappeared in those with blunted HRR.

CONCLUSIONS

In patients with suspected IHD, MPI sensitivity is strongly influenced by the magnitude of patient heart rate increase to the pharmacologic stressor, suggesting an interaction among blunted HRR and lower accuracy in unmasking CAD.

Dobutamine myocardial scintigraphy for the prediction of cardiac events after heart transplantation

BACKGROUND

The long-term outcome after heart transplantation (HTx) is essentially influenced by the occurrence and extent of cardiac allograft vasculopathy (CAV). Single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has been shown to be a useful and cost-effective non-invasive method in patients with known or suspected coronary artery disease, but its role in detecting CAV remains unclear.

AIM

To evaluate the accuracy and predictive value of dobutamine MPI in patients after HTx during a 12-month follow-up.

METHODS

Seventy-seven patients (60 males, 17 females) underwent a total of 216 dobutamine MPI examinations over a period of 5 years. Examinations were obtained an average of 89+/-42 months after orthotopic HTx according to a 1-day protocol using 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) with and without attenuation correction. For the present study, findings from 77 MPI examinations (one MPI examination per patient) were analysed visually and semiquantitatively using a 20-segment model. Summed stress scores (SSS) and summed rest scores (SRS) were calculated and receiver operating characteristic (ROC) analysis was performed to detect optimum threshold values. Patients were followed up for 12 months and cardiac events were registered.

RESULTS

Cardiac events were observed in 10 of the 77 patients. Good interobserver agreement was found for global visual and SRS-/SSS-based analysis (kappa=0.74 and 0.66, respectively). SSS was superior to SRS in the detection of cardiac events. ROC analysis showed an optimized SSS threshold value of three. For predicting a cardiac event during the 12-month follow-up, global visual and semiquantitative analysis reached sensitivities of 90% and 90%, specificities of 72% and 88%, accuracies of 74% and 87%, positive predictive values of 32% and 53% and negative predictive values of 98% and 98%, respectively. The sensitivity, specificity, accuracy and positive and negative predictive values for MPI to detect clinically relevant coronary artery stenoses (> or =50%) at conventional coronary angiography were 83%, 87%, 86%, 56% and 96%, respectively.

CONCLUSIONS

Non-invasive dobutamine MPI reliably identifies patients at risk for subsequent cardiac events in cases of CAV, with a high negative predictive value of 98% and an accuracy of 87%.

Usefulness of Progressive Inhomogeneity of Myocardial Perfusion and Chronotropic Incompetence in Detecting Cardiac Allograft Vasculopathy: Evaluation with Dobutamine Thallium-201 Myocardial SPECT

BACKGROUND

The aim of the study was to investigate the value of longitudinal follow-up of dobutamine thallium-201 single photon emission tomography ((201)Tl SPECT) in the development of significant cardiac allograft vasculopathy (CAV) after orthotopic heart transplantation.

METHODS

We studied 38 cardiac recipients (mean age 57 +/- 12 years) who underwent at least two follow-up dobutamine (201)Tl SPECT since January 1998. All patients had normal coronary angiography and normal left ventricular function initially.

RESULTS

After 2.3 +/- 1.8 years, 12 patients developed significant CAV and there were 4 cardiac deaths (1 died suddenly). Of the 99 scans retrospectively analyzed, patients with significant CAV had elevated values of inhomogeneity score, lung/heart ratio (LHR) at stress and lower left ventricular ejection fraction (all p < 0.05). The higher values of inhomogeneity were significantly correlated with higher stress LHR (r = 0.301, p = 0.021), and lower ejection fraction (r = -0.379, p < 0.001). Progressive inhomogeneity was noted in all heart recipients, and more rapid, although statistically insignificant, in patients who developed significant CAV. Ten patients had inadequate chronotropic response to dobutamine infusion up to 40 mug/kg/min in the follow-up studies. The late onset of chronotropic incompetence was an independent predictor of CAV development (p = 0.03).

CONCLUSIONS

Progressive inhomogeneity of myocardial perfusion, higher lung uptake at stress and chronotropic incompetence assessed by dobutamine (201)Tl myocardial SPECT provide incremental diagnostic value in detecting significant CAV.