Adenosine pharmacologic stress myocardial perfusion tomographic imaging in patients with significant aortic stenosis. Diagnostic efficacy and comparison of clinical, hemodynamic and electrocardiographic variables with 100 age-matched control subjects

Challenges in Diagnosis and Functional Assessment of Coronary Artery Disease in Patients With Severe Aortic Stenosis

More than half of patients with severe aortic stenosis (AS) over 70 years old have coronary artery disease (CAD). Exertional angina is often present in AS-patients, even in the absence of significant CAD, as a result of oxygen supply/demand mismatch and exercise-induced myocardial ischemia. Moreover, persistent myocardial ischemia leads to extensive myocardial fibrosis and subsequent coronary microvascular dysfunction (CMD) which is defined as reduced coronary vasodilatory capacity below ischemic threshold. Therefore, angina, as well as noninvasive stress tests, have a low specificity and positive predictive value (PPV) for the assessment of epicardial coronary stenosis severity in AS-patients. Moreover, in symptomatic patients with severe AS exercise testing is even contraindicated. Given the limitations of noninvasive stress tests, coronary angiography remains the standard examination for determining the presence and severity of CAD in AS-patients, although angiography alone has poor accuracy in the evaluation of its functional severity. To overcome this limitation, the well-established invasive indices for the assessment of coronary stenosis severity, such as fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR), are now in focus, especially in the contemporary era with the rapid increment of transcatheter aortic valve replacement (TAVR) for the treatment of AS-patients. TAVR induces an immediate decrease in hyperemic microcirculatory resistance and a concomitant increase in hyperemic flow velocity, whereas resting coronary hemodynamics remain unaltered. These findings suggest that FFR may underestimate coronary stenosis severity in AS-patients, whereas iFR as the non-hyperemic index is independent of the AS severity. However, because resting coronary hemodynamics do not improve immediately after TAVR, the coronary vasodilatory capacity in AS-patients treated by TAVR remain impaired, and thus the iFR may overestimate coronary stenosis severity in these patients. The optimal method for evaluating myocardial ischemia in patients with AS and co-existing CAD has not yet been fully established, and this important issue is under further investigation. This review is focused on challenges, limitations, and future perspectives in the functional assessment of coronary stenosis severity in these patients, bearing in mind the complexity of coronary physiology in the presence of this valvular heart disease.

Coronary Revascularization in Patients Undergoing Aortic Valve Replacement for Severe Aortic Stenosis

Aortic stenosis (AS) and coronary artery disease (CAD) frequently coexist, with up to two thirds of patients with AS having significant CAD. Given the challenges when both disease states are present, these patients require a tailored approach diagnostically and therapeutically. In this review the authors address the impact of AS and aortic valve replacement (AVR) on coronary hemodynamic status and discuss the assessment of CAD and the role of revascularization in patients with concomitant AS and CAD. Remodeling in AS increases the susceptibility of myocardial ischemia, which can be compounded by concomitant CAD. AVR can improve coronary hemodynamic status and reduce ischemia. Assessment of the significance of coexisting CAD can be done using noninvasive and invasive metrics. Revascularization in patients undergoing AVR can benefit certain patients in whom CAD is either prognostically or symptomatically important. Identifying this cohort of patients is challenging and as yet incomplete. Patients with dual pathology present a diagnostic and therapeutic challenge; both AS and CAD affect coronary hemodynamic status, they provoke similar symptoms, and their respective treatments can have an impact on both diseases. Decisions regarding coronary revascularization should be based on understanding this complex relationship, using appropriate coronary assessment and consensus within a multidisciplinary team.

Coronary Microcirculation in Aortic Stenosis: Pathophysiology, Invasive Assessment, and Future Directions

With the increasing prevalence of aortic stenosis (AS) due to a growing elderly population, a proper understanding of its physiology is paramount to guide therapy and define severity. A better understanding of the microvasculature in AS could improve clinical care by predicting left ventricular remodeling or anticipate the interplay between epicardial stenosis and myocardial dysfunction. In this review, we combine five decades of literature regarding microvascular, coronary, and aortic valve physiology with emerging insights from newly developed invasive tools for quantifying microcirculatory function. Furthermore, we describe the coupling between microcirculation and epicardial stenosis, which is currently under investigation in several randomized trials enrolling subjects with concomitant AS and coronary disease. To clarify the physiology explained previously, we present two instructive cases with invasive pressure measurements quantifying coexisting valve and coronary stenoses. Finally, we pose open clinical and research questions whose answers would further expand our knowledge of microvascular dysfunction in AS. These trials were registered with NCT03042104, NCT03094143, and NCT02436655.

The clinical value and safety of ECG-gated dipyridamole myocardial perfusion imaging in patients with aortic stenosis

The role of vasodilator myocardial perfusion imaging (MPI) for aortic stenosis (AS) is controversial due to safety and accuracy concerns. In addition, its utility after aortic valve (AV) interventions remains unclear. Patients with AS who underwent thallium-201-gated dipyridamole MPI using a cadmium-zinc-telluride camera were retrospectively reviewed and divided into three groups: mild AS, moderate-to-severe AS, and prior AV interventions. Patients with coronary artery disease with ≥50% stenosis, severe arrhythmia, left ventricular ejection fraction (LVEF) <40%, left bundle branch block or no follow-up were excluded. Relationships between the severity of AS, clinical characteristics, hemodynamic response, serious adverse events (SAE) and MPI parameters were analyzed. None of the 47 patients had SAE, including significant hypotension or LVEF reduction. The moderate-to-severe AS group had higher summed stress scores (SSSs) and depressed LVEF than the mild AS group, however there were no differences after AV interventions. SSS was positively correlated with AV mean pressure gradient, post-stress lung-heart ratio (LHRs), and post-stress end-diastolic volume (EDVs) (P < 0.05). In multivariate analysis, LHRs and EDVs were independent contributors to SSS. Dipyridamole-induced ischemia and LV dysfunction is common, and dipyridamole stress could be a safe diagnostic tool in evaluation and follow-up in patients with AS.

Adenosine stress myocardial perfusion imaging in octogenarians: Safety, tolerability, and long-term prognostic implications of hemodynamic response and SPECT-related variables

BACKGROUND

Evaluation of tolerability, safety, and prognostic implications of adenosine stress myocardial perfusion imaging (MPI) in octogenarians.

METHODS

370 octogenarians (49% known coronary artery disease) were studied. Hemodynamic response, MPI-related data, and rest-left ventricular ejection fraction (LVEF) based on echocardiography were registered per patient, and prospective follow-up was performed to document all-cause death (ACD), cardiac death (CD), myocardial infarction (MI), and late revascularization.

RESULTS

No deaths or MIs were observed during adenosine infusion or the short-term post-infusion period. 86% of patients were able to tolerate a 6-minute infusion. All side effects terminated spontaneously after infusion cessation, except for one case of pulmonary oedema. After 9.3 years, there were 124 ACDs, 62 CDs, 16 MIs, and 35 revascularizations. Differences between survival curves of summed stress score (SSS)-based risk groups were significant for all end points (P < .001). SSS and LVEF were independent predictors of all end points (P ≤ .01) and lung uptake of cardiac end points. ΔHR <10 bpm (OR = 1.78, P = .004) and inability to increase HR by >10 bpm and decrease systolic blood pressure by >10 mmHg (OR = 2, P = .02) during adenosine infusion were independent predictors of ACD and CD, respectively. Hemodynamic response variables, SSS, and lung uptake provided incremental prognostic value over pre-test data for ACD and CD.

CONCLUSIONS

In octogenarians, adenosine stress MPI is well tolerated and provides effective long-term risk stratification.

An assessment of the safety, hemodynamic response, and diagnostic accuracy of commonly used vasodilator stressors in patients with severe aortic stenosis

BACKGROUND

Increasing numbers of patients are undergoing transcatheter aortic valve replacement, which often involves assessment of coronary artery disease ischemic burden. The safety and diagnostic accuracy of vasodilator stress agents in patients with severe aortic stenosis (AS) undergoing SPECT myocardial perfusion imaging (MPI) has not been established.

METHODS

Patients with severe AS (valve area <1 cm2) on echocardiography who underwent vasodilator stress SPECT MPI at two centers were identified. Patients with aortic valve intervention prior to MPI or who underwent concurrent exercise during stress testing were excluded. AS patients were matched to controls without AS based on age, gender, BMI, ejection fraction, and stress agent. Symptoms, serious adverse events, hemodynamic response, and correlation to invasive angiography were assessed.

RESULTS

A total of 95 cases were identified with 45% undergoing regadenoson, 31% dipyridamole, and 24% adenosine stress. A significant change in systolic blood pressure (BP), cases vs controls, was observed with adenosine [-17.9 ± 20.1 vs -2.6 ± 24.9 P = .03)], with a trend toward significance with regadenoson [-16.8 ± 20.3 vs -9.4 ± 17.9 (P = .08)] and dipyridamole [-17.8 ± 20.6 vs -9.0 ± 12.1 (P = .05)]. The change in heart rate was significantly different only for adenosine [5.3 ± 16.8 vs 14.2 ± 10.8 (P = .04)]. Overall, 45% of cases vs 24% of controls (P = .004) had a >20 mmHg decrease in systolic BP. Age, BMI, and resting systolic BP were related to a >20 mmHg decrease in systolic BP on univariate analysis, although only higher resting systolic BP was a predictor on multivariate analysis. In 33 patients who underwent angiography, the sensitivity, specificity, and diagnostic accuracy of vasodilator stress MPI was 77%, 69%, and 73%, respectively. No serious adverse events occurred in the severe AS patients.

CONCLUSION

Severe AS patients are more likely to have a hemodynamically significant decrease in systolic BP with vasodilator stress. There were no serious adverse events in this severe AS cohort with good diagnostic performance of MPI compared to angiography.

Coronary Revascularization in Patients Undergoing Transcatheter Aortic Valve Replacement

Concomitant coronary artery disease (CAD) is highly prevalent among patients with severe aortic stenosis (AS). Historically, surgical aortic valve replacement with coronary artery bypass grafting was the only treatment option for patients with severe AS and significant CAD. The rapid expansion of transcatheter aortic valve replacement has led to significant paradigm shifts in the treatment of severe AS and has raised new questions regarding the optimal management of CAD in these patients. We review the evidence regarding management of concomitant CAD in severe AS patients, specifically focusing on issues surrounding transcatheter aortic valve replacement. In the absence of robust evidence supporting specific treatment strategies, decisions regarding coronary revascularization in severe AS should be individualized and made within the context of a multidisciplinary heart team.

Coronary Artery Disease and Symptomatic Severe Aortic Valve Stenosis: Clinical Outcomes after Transcatheter Aortic Valve Implantation

Introduction

The impact of coronary artery disease (CAD) on outcomes after transcatheter aortic valve implantation (TAVI) has not been clarified. Furthermore, less is known about the indication and strategy of revascularization in these high risk patients.

Aims

This study sought to determine the prevalence and prognostic impact of CAD in patients undergoing TAVI, and to assess the safety and feasibility of percutaneous coronary intervention (PCI) before TAVI.

Methods

Patients with severe aortic stenosis (AS) undergoing TAVI were included into a prospective single center registry from 2007 to 2012. Clinical outcomes were compared between patients with and without CAD. In some patients with CAD, it was decided to perform elective PCI before TAVI after decision by the Heart team. The primary endpoints were 30-day and 2-year all-cause mortality.

Results

A total of 91 consecutive patients with mean age of 79 ± 9 years (52% men) underwent TAVI with a median follow-up duration of 16 months (interquartile range of 27.6 months). CAD was present on 46 patients (51%). At 30-day, the incidences of death were similar between CAD and non-CAD patients (9 and 5%, p = 0.44), but at 2 years were 50% in CAD patients and 24% in non-CAD patients [crude hazard ratio with CAD, 2.2; 95% confidence interval (CI), 1.1–4.6; p = 0.04]. Adjusting for age, gender, left ventricular ejection fraction, and glomerular filtration rate, the hazard of death was 2.6-fold higher in patients with CAD (95% CI, 1.1–6.0; p = 0.03). Elective PCI before TAVI was performed in 13 patients (28% of CAD patients). There were no more adverse events in patients who underwent TAVI + PCI when compared with those who underwent isolated TAVI.

Conclusion

In severe symptomatic AS who underwent TAVI, CAD is frequent and adversely impacts long-term outcomes, but not procedure outcomes. In selected patients, PCI before TAVI appears to be feasible and safe.

Stress positron emission tomography is safe and can guide coronary revascularization in high-risk patients being considered for transcatheter aortic valve replacement

BACKGROUND

The safety and accuracy of regadenoson stress positron emission tomography (PET) in patients with significant aortic stenosis (AS) is unknown. In patients undergoing surgical aortic valve replacement, coronary artery bypass grafting for coronary artery disease is standard, but the appropriate revascularization strategy in patients undergoing TAVR is uncertain. Stress PET may identify patients that benefit from revascularization.

METHODS

Fifty consecutive patients who were referred for consideration of TAVR and underwent a stress PET study were retrospectively identified. We assessed major adverse cardiac events and significant decreases in systolic blood pressure. The percentage of jeopardized myocardium was determined by combining ischemic and hibernating myocardium.

RESULTS

Our patients were high risk with a mean Society of Thoracic Surgeons mortality score of 11.4% and had severe AS with a moderately reduced left ventricular ejection fraction (EF) (mean aortic valve area of 0.78 ± 0.25 cm(2) and mean EF of 39 ± 16%). There were no major adverse events during testing. Transient hypotension occurred in 16% of the patients. Revascularization was performed in 44% of patients, and 91% of these patients had revascularization to territories jeopardized on PET. These patients had substantial jeopardized myocardium (median 19%), and only 3 patients underwent revascularization despite less than 10% jeopardized myocardium.

CONCLUSIONS

Stress cardiac PET with regadenoson can be performed safely in patients with severe AS. Results of the PET study can accurately direct subsequent revascularization.

Pre-operative computed tomography coronary angiography to detect significant coronary artery disease in patients referred for cardiac valve surgery

OBJECTIVES

We studied the diagnostic performance of 64-slice computed tomography coronary angiography (CTCA) to rule out or detect significant coronary stenosis in patients referred for valve surgery.

BACKGROUND

Invasive conventional coronary angiography (CCA) is recommended in most patients scheduled for valve surgery.

METHODS

During a 6-month period, 145 patients were prospectively identified from a consecutive patient population scheduled for valve surgery. Thirty-five patients were excluded because of CTCA criteria: irregular heart rhythm (n = 26), impaired renal function (n = 5), and known contrast allergy (n = 4). General exclusion criteria were: hospitalization in community hospital (n = 4), no need for CCA (n = 4), previous coronary artery bypass surgery (n = 1), or percutaneous coronary intervention (n = 4). Of the remaining 97 patients, 27 denied written informed consent. Thus, the study population comprised 70 patients (49 male, 21 female; mean age 63 +/- 11 years).

RESULTS

Prevalence of significant coronary artery disease, defined as having at least 1 > or =50% stenosis per patient, was 25.7%. Beta-blockers were administered in 71%, and 64% received lorazepam. The mean heart rate dropped from 72.5 +/- 12.4 to 59.5 +/- 7.5 beats/min. The mean scan time was 12.8 +/- 1.3 s. On a per-patient analysis, the sensitivity, specificity, and positive and negative predictive values were: 100% (18 of 18; 95% confidence interval [CI] 78 to 100), 92% (48 of 52; 95% CI 81 to 98), 82% (18 of 22; 95% CI 59 to 94), and 100% (48 of 48; 95% CI 91 to 100), respectively.

CONCLUSIONS

The diagnostic accuracy of 64-slice CTCA for ruling out the presence of significant coronary stenoses in patients undergoing valve surgery is excellent and allows CTCA implementation as a gatekeeper for invasive CCA in these patients.

Evaluating the Prevalence of Silent Coronary Artery Disease in Asymptomatic Patients With Spinal Cord Injury

To evaluate the prevalence of coronary artery disease (CAD) in patients with spinal cord injury (SCI), 47 clinically asymptomatic SCI patients received thallium-201 myocardial perfusion single photon emission computed tomography (Tl-201 SPECT) after dipyridamole administration for the diagnosis of CAD. There were 4 groups as follows; group 1: 13 patients with quadriplegia and complete SCI, group 2: 11 patients with quadriplegia and incomplete SCI, group 3: 11 patients with paraplegia and complete SCI, and group 4: 12 patients with paraplegia and incomplete SCI. There were no significant differences in sex distribution, ages, SCI duration, or CAD risk factors among the SCI patients in the 4 groups. All Tl-201 SPECT images were interpreted by the agreement of 2 experienced nuclear medicine physicians without prior knowledge of the patients' histories. A total of 30 of 47 (63.8%) SCI patients had abnormal Tl-201 SPECT findings. Among the 4 groups of SCI patients, those in groups 1 and 4 had the significantly highest and lowest prevalences of abnormal Tl-201 SPECT findings, respectively. We concluded that combined quadriplegia and complete SCI is an important CAD risk factor in SCI patients based on the objective evidence of intravenous dipyridamole cardiac stress testing with Tl-201 SPECT.

Adenosine stress myocardial perfusion tomographic imaging in patients with significant aortic stenosis

BACKGROUND

Myocardial perfusion scintigraphy has been used by some investigators for the diagnosis of coronary artery disease (CAD) in patients with mild, moderate, and moderate to severe aortic stenosis, with various results. The aim of this study was to assess the safety and diagnostic accuracy of adenosine stress myocardial perfusion scintigraphy (adenosine single photon emission computed tomography [Ad-SPECT]) for the detection of CAD in patients with significant aortic stenosis.

METHODS AND RESULT

The study included 75 patients with significant aortic stenosis (maximal instantaneous aortic valve gradient >80 mm Hg [range, 81-149 mm Hg] and aortic valve area <0.75 cm2). All patients underwent Ad-SPECT after a 6-minute infusion of adenosine (140 microg/kg body weight per minute). At the third minute of adenosine infusion, a bolus of 3 mCi thallium 201 was injected, and SPECT acquisition was obtained immediately after completion of adenosine infusion. Coronary angiography was performed in all patients. No major complications during adenosine infusion were observed. All unpleasant symptoms lasted for only a few seconds and did not necessitate cessation of the test. Concerning the angiographically diagnosed CAD, we found that Ad-SPECT showed a sensitivity of 88.6%, a specificity of 72.5%, a positive predictive value of 73.8%, a negative predictive value of 87.8%, and a diagnostic accuracy of 80%.

CONCLUSIONS

Ad-SPECT is a moderately accurate method for detecting the presence or absence of CAD in patients with severe aortic stenosis. However, further modification of this method is required before it can supplant cardiac catheterization in the preoperative evaluation of patients with severe aortic stenosis.

Adenosine myocardial perfusion single photon emission computed tomographic stress testing 24-72 h after uncomplicated myocardial infarction

Safety of performing adenosine myocardial perfusion stress testing as early as 24 h after acute uncomplicated myocardial infarction is not known. We evaluated 31(14 females and 17 males, average age 72, range 46-89 years) consecutive patients with uncomplicated myocardial infarction, who underwent adenosine myocardial perfusion stress imaging, 24-72 h after infarction for risk stratification. Adenosine was infused at a rate of 140 microg/kg/min for 6 min. Twenty patients were presented with non-ST-elevation myocardial infarction. Eleven patients were admitted with acute ST-elevation myocardial infarction. Patients were monitored for signs of complication during and immediately after the stress test. The average time from admission to performance of stress tests was 51 +/- 19 h, ranging from the minimum of 24 h to maximum 72 h. No complications related to adenosine infusion were detected. In conclusion, our data suggest that a further large study of early adenosine myocardial perfusion SPECT imaging may be safe in a carefully selected group of patients after uncomplicated myocardial infarction.

Nuclear cardiology update

This article focuses on the following areas of myocardial perfusion imaging: radiotracer and protocol options, pharmacologic stress agents, and protocols and functional assessment with ECG-gated single photon emission CT.

The higher likelihood of developing cardiomegaly during follow-up in patients with syndrome X and abnormal thallium-201 myocardial perfusion SPECT

'Syndrome X' describes patients with exertional chest pain and a normal coronary arteriogram. In some patients, acute myocardial ischemia can be demonstrated by regional myocardial perfusion defects on thallium-201 exercise test. However, some patients with typical angina have normal perfusion on thallium-201 heart scintigraphy. It is not clear whether there are different prognoses for patients with normal and abnormal thallium studies. In this study, the clinical features, long term follow-up and clinical results of syndrome X patients with normal and abnormal thallium studies were evaluated to determine the differences between these two groups. Fifty-nine patients (52 males, seven females, mean age 62+/-6 years) with syndrome X were enrolled and divided into two groups on the basis of results of thallium-201 heart scintigraphy. Group I was comprised of 22 patients with normal thallium-201 perfusion scan and group II was comprised of 37 patients with abnormal thallium-201 heart scan. All subjects received coronary arteriography, exercise test, thallium-201 myocardial SPECT, ejection fraction of left ventricle, echocardiography, blood analysis and long term follow-up with questionnaire for 10 years. Lower maximal rate-pressure product and higher angina scores were found in group II. More patients developed cardiomegaly (nine of 33 patients) in group II than in group I (one of 21 patients). Both groups, however, were at low risk for cardiac events (cardiac death or myocardial infarction).

Timing of surgery in aortic stenosis

In adults with valvular stenosis, the importance of prompt aortic valve replacement once symptoms occur is well known. The operative mortality for aortic valve replacement has improved dramatically over the past 4 decades and remains the only effective therapy for severe symptomatic aortic stenosis. Aortic valve replacement in patients with left ventricular dysfunction has a high operative mortality, although those patients who do not undergo surgery at all have an even worse outcome. While issues to consider include the presence or absence of coronary artery disease and expected hemodynamics of the prosthetic valve compared with the native valve, when in doubt, one should err on the side of surgical intervention. Elderly age is not a contraindication to aortic valve replacement for severe symptomatic aortic stenosis, although there is a higher prevalence of comorbid disease and higher operative mortality. Life expectancy is significantly prolonged and quality of life is significantly improved in the elderly who survive surgery. Indications for surgery in asymptomatic patients are controversial. We do not recommend valve replacement in asymptomatic patients at this time due to the known risks of surgery and a prosthetic valve and the lack of evidence for benefit of early surgery. Patients undergoing coronary bypass surgery should be considered for concomitant aortic valve surgery for moderate aortic stenosis that is expected to progress to severe stenosis in less than 5 years.

Detection of coronary artery disease in patients with severe aortic stenosis with noninvasive methods

Exercise stress ECG testing is not generally recommended in patients with severe aortic stenosis. Analysis of the utility of exercise testing, both with and without the use of myocardial thallium-201 scintigraphy for the diagnosis of coronary artery disease (CAD), yielded low specificity. A noninvasive, safe, and accurate diagnostic modality to ascertain the presence of CAD is not available to date for patients with severe aortic stenosis. The aim of this study was to assess the safety and diagnostic accuracy of adenosine stress echocardiography (A-Stress-Echo) and of adenosine stress myocardial perfusion scintigraphy (A-SPECT), for the detection of CAD in patients with severe aortic stenosis. The study included 50 patients with severe aortic stenosis (maximal instantaneous aortic valve gradient >80 mmHg, range 81 to 144 mmHg, and aortic valve area <0.75 cm2). All patients were submitted to A-Stress-Echo, after a 6-minute infusion of adenosine (140 microg/kg body weight/min), and then (>3 days later) A-SPECT with the same dosage of adenosine as above. Coronary angiography was performed in all patients. No major complications were observed. The unpleasant symptoms were brief and did not necessitate cessation of the test. Both modalities showed the same sensitivity (85% for A-SPECT and 85% for A-Stress-Echo) angiographically diagnosed CAD while A-Stress-Echo yielded much higher specificity (96.7% vs 76.7%). Concordance of the two methods was found in 40 cases and the specificity for those patients was 100%. A-Stress-Echo and A-SPECT, either separately or in combination, constitute excellent and safe noninvasive diagnostic methods in detecting CAD in patients with severe aortic stenosis.

Aortic stenosis. Clinical evaluation and optimal timing of surgery

Aortic valve disease is common in the elderly with recent data suggesting that aortic sclerosis and stenosis are the end-stage of an active disease process. Aortic atenosis may be diagnosed at symptom onset (angina, heart failure or syncope) but often the diagnosis is suspected in an asymptomatic patient with a systolic murmur. The diagnosis can be confirmed and disease severity evaluated reliably using Doppler echocardiography. Symptomatic severe aortic stenosis is treated with valve replacement, even in the elderly, due to the extremely poor prognosis without relief of outflow obstruction. Management is controversial when there is coexisting moderate aortic stenosis and left ventricular systolic dysfunction.