Direct comparison between pharmacological stress with adenosine triphosphate disodium and exercise stress myocardial perfusion imagings

Comparative evaluation of a novel [18F] F-Labeled PET tracer XTR004 against [13N] ammonia in myocardial perfusion imaging for coronary artery disease

AIMS

This study aimed to evaluate image quality, myocardial perfusion, and diagnostic performance of a novel [18F]F-labeled PET tracer, XTR004 PET, myocardial perfusion imaging (MPI) compared with [13N]Ammonia (NH3) PET MPI.

METHODS AND RESULTS

Forty-seven patients with suspected or known coronary artery disease (CAD) were prospectively enrolled to undergo one-day rest/ATP-stress XTR004 and NH3 electrocardiograph-gated PET imaging within 2 weeks. Among them, twenty-six patients underwent invasive coronary angiography (ICA), and nineteen were identified with flow-limited CAD (stenosis ≥ 70%). Image quality (excellent/good/average) and certainty of interpretation were evaluated by two independent, blinded readers. Despite a higher liver uptake, XTR004 achieved good to excellent image quality in 83% of cases, comparable to 95.7% of NH3(P = 0.091). Additionally, the diagnostic certainty, measured as the percentage of cases with definitely abnormal or normal interpretations, was similar between XTR004 and NH3, with results of 87.2% and 89.2%, respectively. The sensitivity and specificity levels of XTR004 and NH3 MPI were similar (79% vs. 79%, 86% vs. 71%, P = 1.00). Linear regression of rest/stress myocardial perfusion in 17 segments revealed the linear slope close to unity with excellent R2 value (rest: slope = 0.954-1.074, R2 = 0.990-0.997; stress: slope = 0.951-1.082, R2 = 0.971-0.996). XTR004 was tolerated well by all patients. No adverse events were reported.

CONCLUSION

XTR004 PET MPI demonstrated promising image quality, diagnostic certainty and myocardial perfusion characteristics comparable to NH3 PET MPI. Future research should concentrate on the quantitative analysis of myocardial blood flow to explore the clinical implications of XTR004 PET MPI.

Short-duration, submaximal intensity exercise stress combined with adenosine triphosphate decreases artifacts in myocardial perfusion single-photon emission computed tomography

BACKGROUND

Myocardial perfusion single-photon emission computed tomography (SPECT) imaging with stress is a useful examination for detecting coronary artery disease. Since the presence of artifacts is remaining challenges, we aimed to define the minimum intensity of low-grade exercise stress levels combined with drug stress to reduce undesired artifacts and their related factors.

METHODS

We divided patients with suspicious coronary artery disease into 4 groups as follows: group A, adenosine triphosphate (ATP) for 6 min; group A + 25 W, ATP + 25 W exercise for 6 min; group A + 35 W, ATP + 35 W exercise for 6 min; group A + 45 W, ATP + 45 W exercise for 6 min) and enrolled only those whose summed stress scores were < 3. Undesired artifacts were evaluated on the basis of heart-to-liver activity (H/L) ratio and heart-to-10 pixels below the heart (H/below the H) ratio.

RESULTS

The logarithmic values of H/L and H/below the H ratios were significantly higher in groups A + 35 W and A + 45 W than in group A (p < 0.05, each). In all the patients, the logarithmic values of H/L and H/below the H ratios positively correlated with the increment of rate pressure product (RPP, p = 0.002 and p = 0.005, respectively) after stress in the univariate analysis. The left ventricular end-diastolic volume (LVEDV) after stress (p = 0.002) negatively correlated with the logarithmic value of H/below the H ratio, but not H/L ratio. Although the increment of RPP was independently associated with the logarithmic values of both H/L (p = 0.001) and H/below the H ratios (p = 0.005), LVEDV was also independently associated with the logarithmic value of H/below the H ratio (p < 0.001) in multivariate regression analysis under adjusting with age and sex.

CONCLUSION

ATP plus ≥35 W exercise stress for 6 min was useful for reducing undesired artifacts after stress in myocardial perfusion SPECT. LVEDV after stress in addition to the increment of RPP was independently associated with the H/below the H ratio, but not the H/L ratio.

Cardiac Magnetic Resonance Versus Single-Photon Emission Computed Tomography for Detecting Coronary Artery Disease and Myocardial Ischemia: Comparison with Coronary Angiography

Background: This study aimed to compare the diagnostic accuracy of stress single-photon emission computed tomography (SPECT) and stress cardiac magnetic resonance (CMR) for the assessment of coronary artery disease (CAD) in the same patients, using coronary angiography as the reference standard. Methods: Thirty patients with known or suspected CAD who were referred for exercise SPECT myocardial perfusion imaging (MPI) for the evaluation of myocardial ischemia underwent stress CMR MPI and computed tomography coronary angiography (CTCA) or selective coronary angiography (SCA). The data from the two stress modalities were compared against the data from angiography. Results: In our study population, 30% of the recruited subjects had significant CAD. The CMR sensitivity for the detection of significant CAD and/or myocardial ischemia was 89% and specificity was 76%. For SPECT, the corresponding sensitivity was 78% and specificity was 52%. The negative predictive value was 92% for CMR and 83% for SPECT. The receiver-operating characteristic (ROC) analysis evaluating the presence of significant CAD, CMR (area under the curve (AUC) 0.78) outperformed SPECT (AUC 0.59) (p < 0.01). The ROC analysis evaluating the presence of myocardial ischemia was also in favor of CMR (AUC 0.82) versus SPECT (AUC 0.67) (p < 0.01). Conclusions: CMR has high diagnostic accuracy for the detection of CAD and stress-induced ischemia and appears to outperform SPECT. CMR may thus be the preferred noninvasive imaging modality to assess patients with known or suspected CAD.

Adenosine triphosphate (ATP) and adenosine cause similar vasodilator effect in patients undergoing stress perfusion cardiac magnetic resonance imaging

To evaluate the vasodilator effect of adenosine triphosphate (ATP) compared with adenosine in stress perfusion cardiac magnetic resonance (CMR) examinations. A total of thirty-three patients underwent clinically indicated stress/rest perfusion CMR examination following intravenous injection of a total dose of 0.2 mmol/kg of gadobutrol. Individuals were randomly assigned to ATP (160 mcg/kg/min) or adenosine (140 mcg/kg/min). The vasodilator effect of both drugs was analyzed by comparing differences in heart rate, symptoms during stress, and semiquantitative myocardial and splenic perfusion parameters, including time, time to peak, upslope, myocardial perfusion reserve index, tissue perfusion values, splenic and myocardial signal intensity ratios, and splenic-to-myocardial signal intensity ratios. No significant difference was found in heart rate variation between the stressors (26.1 ± 19.1 bpm for ATP vs. 21.7 ± 17.3 bpm for adenosine, p = 0.52). Patients receiving ATP referred less pronounced clinical symptoms. Semiquantitative myocardial perfusion parameters were comparable, and patients in the adenosine and ATP groups showed similar myocardial perfusion reserve index values (2.34 [1.62-2.73] vs 1.63 [1.29-2.10], p = 0.07). Splenic switch off was visually confirmed in all patients and estimated spleen to myocardium ratio was similar (0.92 [0.53-1.09] vs 0.81 [0.53-0.86] with ATP and adenosine, respectively, p = 0.12). Both ATP and adenosine are potent coronary vasodilators that can be safely employed in stress-CMR. Both stressor cause similar hyperemic response. Splenic switch-off can be used to assess stress adequacy in patients undergoing stress-CMR with either adenosine or ATP.