Pharmacologic manipulation of coronary vascular physiology for the evaluation of coronary artery disease

Development and validation of a hydrophilic interaction liquid chromatography-tandem mass spectrometry method for the quantification of regadenoson in human plasma and its pharmacokinetic application

Regadenoson, the first selective adenosine A_2A receptor agonist, is used to perform exercise stress test during radionuclide myocardial perfusion imaging. To detect the concentration of regadenoson in human plasma, a simple, fast, and sensitive tandem mass spectrometry method was established herein. Acetonitrile was used as a protein precipitation agent. Chromatographic separation was completed in 6.5 min using a BEH HILIC column (50 × 2.1 mm, 1.7 μm). The mobile phase consisted of 10 mmol/L ammonium acetate/acetonitrile (gradient elution). To quantify regadenoson and regadenoson-d3, an API 4000 mass spectrometry in multiple reaction monitoring mode with transitions of 391.3→259.2 and 394.3→262.2, respectively, was utilized. The calibration curve was linear in the range of 0.100-50.0 μg/L, and the intrabatch and interbatch precisions were <9.7% and <13.0%, respectively, and the accuracy was 2.0-6.9%. There was no apparent matrix effect for regadenoson or regadenoson-d3. The developed method was used to study the pharmacokinetic characteristics of regadenoson in healthy Chinese subjects.

Changes in left ventricle myocardial volume during stress test using cadmium-zinc-telluride cardiac imaging: Implications in coronary artery disease

BACKGROUND

Cadmium-zinc-telluride (CZT) SPECT allows the estimation of left ventricle myocardial volume (LVMV). We tested the clinical relevance of rest-stress LVMV changes (Δ LVMV) in detecting coronary artery disease (CAD, coronary stenosis > 70%), using CZT-SPECT.

METHODS

We prospectively enrolled 512 consecutive patients with known or suspected CAD (mean age: 70.3 ± 9.2 years, 72% male) for stress-rest myocardial perfusion imaging (MPI, single-day stress-rest protocol). We quantified summed stress scores (SSS), summed rest scores, and summed difference scores, together with LVMV and ejection fraction (EF) after stress and at rest. All patients underwent coronary angiography within 30 days.

RESULTS

Two hundred seventy-two patients had CAD at coronary angiography. ΔLVMV ≤ 5 mL, corresponding to 6% of change from rest LVMV, was the best predictor of CAD (AUC = 0.831, 79% sensitivity, 82% specificity), irrespective of the stress protocol (dipyridamole or exercise stress) and independently of MPI-SSS, LV EF, and clinical history (P = 0.004). Integrated discrimination improvement (IDI) and net reclassification improvement (NRI) were significant for the addition of ΔLVMV ≤ 5 mL (IDI = 6.1%, P < 0.0001; NRI = 29.7%, P = 0.02) to MPI-SSS, whereas the other parameters were not.

CONCLUSIONS

The evaluation of ΔLVMV using CZT-SPECT can improve the diagnostic accuracy in predicting the presence of CAD when added to conventional MPI.

Higher incidence of vasodilator-induced left ventricular cavity dilation by PET when compared to treadmill exercise-ECHO in hypertrophic cardiomyopathy

BACKGROUND

Vasodilator-induced transient left ventricular cavity dilation (LVCD) by positron emission tomography (PET) is associated with microvascular dysfunction in hypertrophic cardiomyopathy (HCM). Here we assessed whether HCM patients who develop LVCD by PET during vasodilator stress also develop LV cavity dilation by echocardiography (ECHO-LVCD) following exercise stress.

METHODS

A retrospective analysis of cardiac function and myocardial blood flow (MBF) was conducted in 108 HCM patients who underwent perfusion-PET and exercise-ECHO as part of their clinical evaluation. We performed a head-to-head comparison of LV volumes and ejection fraction (LVEF) at rest and stress (during vasodilator stress, post-exercise), in 108 HCM patients. A ratio > 1.13 of stress to rest LV volumes was used to define PET-LVCD, and a ratio > 1.17 of stress to rest LVESV was used to define ECHO-LVCD. Patients were divided into 2 groups based on the presence/absence of PET-LVCD. MBF and myocardial flow reserve were quantified by PET, and global longitudinal strain (GLS) was assessed by ECHO at rest/stress in the two groups.

RESULTS

PET-LVCD was observed in 51% (n = 55) of HCM patients, but only one patient had evidence of ECHO-LVCD (ratio = 1.36)-this patient also had evidence of PET-LVCD (ratio = 1.20). The PET-LVCD group had lower PET-LVEF during vasodilator stress, but ECHO-LVEF increased in both groups post-exercise. The PET-LVCD group demonstrated higher LV mass, worse GLS at rest/stress, and lower myocardial flow reserve. Incidence of ischemic ST-T changes was higher in the PET-LVCD group during vasodilator stress (42 vs 17%), but similar (30%) in the two groups during exercise.

CONCLUSION

PET-LVCD reflects greater degree of myopathy and microvascular dysfunction in HCM. Differences in the cardiac effects of exercise and vasodilators and timing of stress-image acquisition could underlie discordance in ischemic EKG changes and LVCD by ECHO and PET, in HCM.

Blood haemoglobin, renal insufficiency, fractional flow reserve and plasma NT-proBNP is associated with index of microcirculatory resistance in chronic coronary syndrome

BACKGROUND

Coronary microvascular dysfunction (CMVD) is associated with adverse cardiovascular outcome. We aimed to determine the prevalence of CMVD and factors related to index of microcirculatory resistance (IMR) in consecutive patients with chronic coronary syndrome (CCS) undergoing elective coronary angiography.

METHODS AND RESULTS

Non-interventional physicians enrolled 274 patients with CCS before angiography, to minimize selection bias by PCI-operators. Fractional flow reserve (FFR) and IMR were measured in the LAD. Subjects with extensively diseased LAD, no measures due to technical reasons or violation of protocol were excluded from the analysis (n = 54). The proportion of patients with IMR corrected for collateral flow (IMR_corr) >25 units was 25% (95% confidence interval [CI] 19%-31%) in all 220 patients. In subjects with FFR ≤0.80 in the LAD the proportion of IMR_corr > 25 units was 21% (95% CI 13%-30%) as compared to subjects with FFR >0.80, 29% (95% CI 21%-36%), p = .268. Haemoglobin (p < .005; r2 = 0.084), FFR in the LAD (p = .001; r2 = 0.049), creatinine clearance (p = .001; r² = 0.049; inversely), and NT-proBNP (p = .038; r² = 0.021) were independently associated with IMR_corr in multivariate linear regression analysis.

CONCLUSIONS

We report that IMR_corr is associated with renal dysfunction, NT-proBNP, FFR in the LAD and, for the first time, blood haemoglobin. One in four of patients referred for coronary angiography due to CCS have CMVD defined as IMR_corr > 25 in the LAD.

Safety of regadenoson stress testing in patients with pulmonary hypertension

OBJECTIVES

We sought to determine the safety of regadenoson stress testing in patients with PH.

BACKGROUND

PH is increasingly recognized at more advanced ages. As many as one-third of patients with PH have coronary artery disease. Because of their physical limitations, patients with PH are unable to adequately exercise. Regadenoson can potentially have an adverse impact due to their tenuous hemodynamics. Current guidelines suggest performing a coronary angiography in patients with PH who have angina or multiple coronary risk factors.

METHODS

We identified 67 consecutive patients with confirmed PH by catheterization (mean PA > 25 mmHg not due to left heart disease) who underwent MPI with regadenoson stress. Medical records were reviewed to determine hemodynamic and ECG response to regadenoson.

RESULTS

No serious events occurred. Common side effects related to regadenoson were observed, dyspnea being the most common (70.6%). No syncope occurred. Heart rate increased from 74.6 ± 14 to 96.3 ± 18.3 bpm, systolic blood pressure increased from 129.8 ± 20.9 to 131.8 ± 31 mmHg, and diastolic blood pressure decreased from 77.1 ± 11.4 to 72.9 ± 15.3 mmHg. There was no ventricular tachycardia, ventricular fibrillation, or second- or third-degree atrioventricular block.

CONCLUSION

Regadenoson stress MPI appears to be well tolerated and safe in patients with PH.

Influence of hemodialysis on regadenoson clearance in an in vitro hemodialysis model

BACKGROUND

Regadenoson is a novel pharmacological stress agent whose disposition during hemodialysis is not known. The purpose of this study was to determine the clearance of regadenoson under varying dialytic conditions using an in vitro hemodialysis model.

METHODS AND RESULTS

Whole human blood was used to analyze the effect of hemodialysis on the clearance of regadenoson. Regadenoson transmembrane clearance (CLD) was assessed for both a standard permeability and a high permeability polysulfone hemodialyzer with blood/dialysate flow rates of 300/600 and 400/800 mL/min. A two-tailed, paired Student's t test was used to compare regadenoson CLD between hemodialyzer types and flow rates. The mean ± SD regadenoson CLD values ranged between 62.5 ± 11.8 and 89.1 ± 24.0 mL/min for all dialytic conditions. There was no significant difference in regadenoson CLD between hemodialyzer types and flow rates (p > .05).

CONCLUSIONS

Hemodialysis enhances the clearance of regadenoson independent of hemodialyzer permeability and blood/dialysate flow rate. This clearance is modest relative to total body clearance and is unlikely to produce a clinically significant outcome.

Clinical value of hyperemic left ventricular systolic function in vasodilator stress testing

Exercise results in increased left ventricular contractility in normal individuals. Similar changes can also be seen with vasodilator stress. This article discusses the physiologic basis of these changes as well as reviews the clinical data supporting the use of these parameters for diagnostic and prognostic evaluation. Methodologic limitations as well as other concomitant pathologic processes which may confound interpretation of stress-induced changes in LVEF are also reviewed.

Abnormal origins of the coronary arteries from the aortic root

Anomalous origin of a coronary artery from the aorta is a potentially serious anomaly that occurs in about 0.1-0.2% of the population. This percentage is small; however, it translates into about 4000 annual births with these anomalies. The clinical presentation of these anomalies is rare, and hence most are and will remain asymptomatic. The various anatomic anomalies are described, with anomalous origin of the left coronary artery that then passes between the aorta and pulmonary artery being the most serious of these anomalies. The pathophysiology resulting from these anomalies is described, as are methods for identifying those who require treatment; however, we still do not know the best methods of determining which patients need treatment.