Incremental prognostic value of coronary flow reserve derived from SPIM digital positron emission tomography

Introduction

Positron emission tomography (PET) myocardial perfusion imaging (MPI) is an established test in the diagnosis and prognosis of patients with cardiac diseases. Silicon photomultiplier (SiPM) digital PET is the latest advancement in this technology with improved detector sensitivity, coincidence time resolution, and spatial resolution, allowing for Sub-milliSievert cardiac PET MPI.

Purpose

We aimed to assess the independent and incremental prognostic value of SiPM digital PET derived coronary flow reserve (CFR) to clinical and nuclear variables.

Methods

Consecutive patients who had clinically indicated digital Rubidium PET MPI were included. Rubidium dose was 10–20 mCi according to patient's weight. Patients were followed from the date of imaging to incident major adverse cardiovascular event (MACE: inclusive of all-cause death, myocardial infarction, admission for heart failure and late revascularization – percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) >90 days after imaging).

Results

The study population consisted of 2,893 patients with clinically indicated PET MPI (mean age 67 (±12), 53% male, 41% Caucasian). Cardiovascular risk factors were prevalent (88% hypertensive, 80% dyslipidemic, 47% diabetics, 18% ever smoking). After a mean follow-up of 8±7 months, 250 patients (8.6%, 10.7 per 1000 person-year) experienced MACE (90 D / 38 MI / 51 PCI / 11 CABG / 113 HF). In nested multivariable cox models, CFR was independently associated with incident MACE (HR 0.38, 95% CI 0.29–0.51, p<0.001) and incrementally improved risk prediction (Harrell's C=0.77, p=0.002).

Conclusion

Our findings showed that a Sub-milliSievert SiPM digital PET-derived CFR provided incremental value in risk-stratifying patients and identifying those at increased risk of incident outcomes.

Funding Acknowledgement

Type of funding sources: None.

Prognostic value of PET derived coronary flow reserve: should we correct for resting perfusion product?

Introduction

Positron emission tomography (PET) myocardial perfusion imaging (MPI) derived coronary flow reserve (CFR) is an important risk-stratifying tool to tailor management of patients with coronary artery disease. Resting myocardial blood flow (MBF) is positively correlated to the product of resting heart rate and systolic blood product (resting pressure product – RPP), and can in turn lead to lower CFR in the setting of normal stress MBF.

Purpose

We aimed to assess the comparative incremental prognostic value of uncorrected to RPP-corrected CFR in predicting incident events.

Methods

Consecutive patients who had clinically indicated PET MPI were included. Patients were followed from the date of imaging to incident major adverse cardiovascular event (MACE: inclusive of all-cause death, myocardial infarction, admission for heart failure and late revascularization – percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) >90 days after imaging).

Results

The study population consisted of 2,893 patients with clinically indicated PET MPI (mean age 67 (±12), 53% male, 41% Caucasian). Cardiovascular risk factors were prevalent (88% hypertensive, 80% dyslipidemic, 47% diabetics, 18% ever smoking). After a mean follow-up of 8±7 months, 250 patients (8.6%, 10.7 per 1000 person-year) experienced MACE (90 D/38 MI/51 PCI/11 CABG/113 HF). Both uncorrected and corrected CFR were independently associated with incident MACE (HR 0.38, 95% CI 0.29–0.51, p<0.001 and 0.61, 95% CI 0.50–0.76, p<0.001 respectively). A comparison of model incremental prognostic value showed the model with uncorrected CFR had a statistically higher Harrell's C (0.76 vs 0.77, p=0.23).

Conclusion

Our findings showed that the prognostic value of CFR was preserved even in the setting of high resting blood pressure or heart rate. This suggests that correction for RPP should be selective.

Funding Acknowledgement

Type of funding sources: None.

Coronary microvascular health in patients with prior COVID-19 infection and no known CAD

Introduction

Although most patients recovering from acute COVID-19 infection have complete resolution of symptoms, some have cardiopulmonary symptoms lingering long after the acute phase of the disease. One proposed mechanism involves chronicity of COVID-19 associated with myocarditis and endotheliopathy.

Purpose

To determine the coronary microvascular health of patients with prior COVID-19 and no known coronary artery disease (CAD) using positron emission tomography (PET).

Methods

Cases consisting of patients without known CAD but previous COVID-19 infection who had clinically indicated PET imaging were matched 1:4 on clinical and cardiovascular risk factors to controls having no prior COVID-19 infection. Myocardial blood flow (MBF) in ml/gm/min was obtained from dynamic images at rest and peak hyperemia. The coronary flow reserve (CFR) was calculated as the ratio of stress to rest MBF of the left ventricle. Coronary microvascular dysfunction (CMD) was defined as CFR<2.

Results

The study population consisted of 315 patients, 25% (n=80) of which had prior COVID-19 infection (mean±SD age 64±11 years, 46% men). The median (IQR) number of days between COVID-19 infection and PET imaging was 190 (85–268) days. After adjusting for age, gender and cardiovascular risk factors, patients with prior COVID-19 and no known CAD had a statistically significant higher odds of having a CFR <2 (OR 4.9, 95% CI 2.3–10.1 p<0.001) and CFR <2 normalized to patient's rate-systolic blood pressure product (OR 2.8, 95% CI 1.6–5.0 p=0.001). The annualized event rate for the composite outcome of all-cause death, myocardial infarction, admission for heart failure exacerbation and late revascularization was higher in cases vs controls and in those with CMD.

Conclusion

Our analysis showed that patients with prior COVID-19 and no known CAD had higher rates of CMD, and that the presence of CMD was associated with higher risk of incident cardiovascular events.

Funding Acknowledgement

Type of funding sources: None.

Relation between clinical, angiographic and ischemic findings at baseline and ischemia-related adverse outcomes at 1 year in the Asymptomatic Cardiac Ischemia Pilot study. ACIP Study Group

OBJECTIVES

We attempted to investigate the relation between patient characteristics and adverse outcome in patients with ischemia and clinically stable coronary artery disease (CAD).

BACKGROUND

Evidence suggests that cardiac ischemia, detected by exercise stress testing (ETT) and ambulatory electrocardiographic (AECG) monitoring during daily living, identifies a subgroup of patients at increased risk for adverse outcome, but the relation between these ischemia findings and clinical and angiographic characteristics is largely unknown.

METHODS

We examined the relation between clinical, angiographic and ischemia characteristics at entry with adverse outcome observed at 1 year in the 558 patients enrolled in the Asymptomatic Cardiac Ischemia Pilot (ACIP) study.

RESULTS

By the 12-month visit 13.1% of patients had an ischemia-related adverse clinical outcome that included death, nonfatal myocardial infarction or an ischemia-related hospital admission. Multivariate analysis identified only the number of AECG ischemic episodes at entry (odds ratio [OR] 1.06, 99% confidence interval [CI] 1.01 to 1.12, p = 0.002) as an independent predictor of outcome. Assignment to revascularization (as opposed to an initial medical treatment strategy) showed a trend (OR 0.56, 99% CI 0.26 to 1.2, p = 0.05). None of the other baseline clinical, exercise or angiographic variables examined provided additional information relative to adverse outcome.

CONCLUSIONS

Determinants of adverse outcome, among clinically stable patients with CAD and ischemia induced by stress and daily life were magnitude of AECG ischemia before treatment and, possibly, initial treatment assignment. Among the many other characteristics examined, including age, symptom status and angiographic and exercise variables, none contributed additional independent prognostic information. These two simple variables, which may be modifiable, need further study in a larger trial.

Asymptomatic Cardiac Ischemia Pilot (ACIP) study: effects of coronary angioplasty and coronary artery bypass graft surgery on recurrent angina and ischemia. The ACIP investigators

OBJECTIVES

The Asymptomatic Cardiac Ischemia Pilot (ACIP) study showed that revascularization is more effective than medical therapy in suppressing cardiac ischemia at 12 weeks. This report compares the relative efficacy of coronary angioplasty or coronary artery bypass graft surgery in suppressing ambulatory electrocardiographic (ECG) and treadmill exercise cardiac ischemia between 2 and 3 months after revascularization in the ACIP study.

BACKGROUND

Previous studies have shown that coronary angioplasty and bypass surgery relieve angina early after the procedure in a high proportion of selected patients. However, alleviation of ischemia on the ambulatory ECG and treadmill exercise test have not been adequately studied prospectively after revascularization.

METHODS

In patients randomly assigned to revascularization in the ACIP study, the choice of coronary angioplasty or bypass surgery was made by the clinical unit staff and the patient.

RESULTS

Patients assigned to bypass surgery (n = 78) had more severe coronary disease (p = 0.001) and more ischemic episodes (p = 0.01) at baseline than those assigned to angioplasty (n = 92). Ambulatory ECG ischemia was no longer present 8 weeks after revascularization (12 weeks after enrollment) in 70% of the bypass surgery group versus 46% of the angioplasty group (p = 0.002). ST segment depression on the exercise ECG was no longer present in 46% of the bypass surgery group versus 23% of the angioplasty group (p = 0.005). Total exercise time in minutes on the treadmill exercise test increased by 2.4 min after bypass surgery and by 1.4 min after angioplasty (p = 0.02). Only 10% of the bypass surgery group versus 32% of the angioplasty group still reported angina in the 4 weeks before the 12-week visit (p = 0.001).

CONCLUSIONS

Angina and ambulatory ECG ischemia are relieved in a high proportion of patients early after revascularization. However, ischemia can still be induced on the treadmill exercise test, albeit at higher levels of exercise, in many patients. Bypass surgery was superior to coronary angioplasty in suppressing cardiac ischemia despite the finding that patients who underwent bypass surgery had more severe coronary artery disease.

Events in the Cardiac Arrhythmia Suppression Trial (CAST): mortality in patients surviving open label titration but not randomized to double-blind therapy

The patient characteristics and outcomes were studied in the 318 patients who survived open label drug titration in the Cardiac Arrhythmia Suppression Trial (CAST) and who were not randomized to double-blind therapy and in 942 patients, who were randomized to double-blind placebo therapy. The patients randomized to placebo therapy had a lower total mortality or resuscitated cardiac arrest rate (4% vs. 8.5%). However, at baseline, nonrandomized patients were dissimilar from patients randomized to placebo in the following ways: older; lower left ventricular ejection fraction; greater use of digitalis, diuretic drugs and antihypertensive agents; lesser use of beta-adrenoceptor blocking agents and more frequent prior cardiac problems, including runs of ventricular tachycardia and left bundle branch block. A matched comparison that took these inequities into account showed no significant differences in mortality or rate of resuscitation from cardiac arrest between nonrandomized patients and clinically equivalent patients randomized to placebo. Cox regression analysis indicated that two factors significantly increased the hazard ratio for arrhythmic death or resuscitated cardiac arrest in the nonrandomized patients: female gender (4.7, p less than 0.05) and electrocardiographic events (ventricular tachycardia, proarrhythmia, widened QRS complex, heart block, bradycardia) during open label titration (7.0, p less than 0.005). However, some potentially important differences between men and women were not included in the Cox regression model. Of the nonrandomized patients, approximately 70% were not randomized because of lack of suppression of ventricular premature depolarizations or adverse events, or both, and the remaining 30% because of patient or private physician request with no indication of another reason.(ABSTRACT TRUNCATED AT 250 WORDS)

The inverse relationship between baseline left ventricular ejection fraction and outcome of antiarrhythmic therapy: a dangerous imbalance in the risk-benefit ratio

Each year, millions of prescriptions are written for antiarrhythmic drug suppression of ventricular arrhythmias. A large portion of these prescriptions are written for patients with asymptomatic, complex ventricular arrhythmias and organic heart disease, termed "potentially malignant" or "potentially lethal." Since arrhythmia suppression in this population is of unproven benefit, we performed the following study: A total of 246 patients (42% with significant left ventricular dysfunction) had complex ventricular arrhythmias, and were treated with one of eight antiarrhythmic drugs (Vaughan Williams classes IA, IB, IC, II, and III). The extent of arrhythmia suppression and the development of serious complications resulting from therapy after 2 weeks was of primary interest. A total of 82 of 246 (33%) maintained adequate (protocol definition) suppression of both ventricular premature beats (VPBs) as well as nonsustained ventricular tachycardia (VT) for 2 weeks, mostly in patients with left ventricular ejection fraction (LVEF) greater than or equal to 40% (p = 0.04 versus LVEF less than 40%). Life-threatening complications of antiarrhythmic therapy occurred most frequently in the 61 patients with an LVEF less than 30% compared to the 185 patients with LVEF greater than or equal to 30% (15% versus 2.1%, p = 0.0005). Suppression of VT was achieved nearly twice as commonly in patients with an LVEF greater than or equal to 30% than in those with an LVEF less than 30% (67% versus 36%; p = 0.0008). Life-threatening complications occurred seven times as frequently in patients presenting with nonsustained VT and an LVEF less than 30% (18% versus 2.3%; p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)