Determinants of coronary flow reserve in heart transplantation: a study performed with contrast-enhanced echocardiography

Sex differences in diagnostic modalities of coronary artery disease: Evidence from coronary microcirculation

Although atherosclerosis is usually considered a disease of the large arteries, risk factors for atherosclerosis also trigger structural and functional abnormalities at a microvascular level. In cardiac disease, microvascular dysfunction is especially relevant in women, among whom the manifestation of ischemic disease due to impaired coronary microcirculation is more common than in men. This sex-specific clinical phenotype has important clinical implications and, given the higher pre-test probability of coronary microvascular dysfunction in females, different diagnostic modalities should be used in women compared to men. In this review, we summarize invasive and non-invasive diagnostic modalities to assess coronary microvascular function, ranging from catheter-based evaluation of endothelial function to Doppler echocardiography and positron emission tomography. Moreover, we discuss different clinical settings in which microvascular disease plays an important role, underlining the importance of choosing the right diagnostic modality depending on the sex of the patients.

Does Patient Compliance Influence Wearable Cardioverter Defibrillator Effectiveness? A Single-Center Experience

The study was designed to assess patient adherence to wearable cardioverter defibrillator as an indicator of device effectiveness. The patient training is not widely properly standardized. We enrolled 25 patients with a wearable cardioverter defibrillator to prevent sudden cardiac death between June 2020 and August 2022. Among them, 84% were male with a median age of 63.6 years. The indication was an ischemic (44%) and a non-ischemic (56%) disease. The patients were followed-up until the decision to upgrade to an implantable device was taken. We trained the patients according to our suggested protocol. The median wear time was 90 days, and the median daily wear time was 23.5 h, similar throughout sex, age, and indication groups. In total, 24% of the participants underwent cardioverter defibrillator implantation. Between the device-implanted and non-implanted groups, left ventricular ejection fraction and left ventricular indexed end-diastolic volume were significantly different (EF 35.8 ± 12 vs. 46.4 ± 8.5%, p = 0.028, iEDV 108 ± 52 vs. 70.7 ± 21.1 mL/m2, p = 0.024). We did not find any differences in cardiac magnetic resonance data, even though all patients who underwent device implantation had late gadolinium enhancement spots. Our results support standardized patient training to obtain great patient adherence to the instructions to the wearable device and therefore its effectiveness.

Depression in Heart Failure with Reduced Ejection Fraction, an Undervalued Comorbidity: An Up-To-Date Review

Introduction: Depression is a common and severe comorbidity among individuals with heart failure (HF). Up to a third of all HF patients are depressed, and an even higher proportion have symptoms of depression. Aim: In this review, we evaluate the relationship between HF and depression, explain the pathophysiology and epidemiology of both diseases and their relationship, and highlight novel diagnostic and therapeutic options for HF patients with depression. Materials and Methods: This narrative review involved keyword searches of PubMed and Web of Science. Review search terms included ["Depression" OR "Depres*" OR "major depr*"] AND ["Heart Failure" OR "HF" OR "HFrEF" OR "HFmrEF" OR "HFpEF" OR "HFimpEF"] in all fields. Studies included in the review met the following criteria: (A) published in a peer-reviewed journal; (B) described the impact of depression on HF and vice versa; and (C) were opinion papers, guidelines, case studies, descriptive studies, randomized control trials, prospective studies, retrospective studies, narrative reviews, and systematic reviews. Results: Depression is an emergent HF risk factor and strongly relates with worse clinical outcomes. HF and depression share multiple pathways, including platelet dis-reactivity, neuroendocrine malfunction, inappropriate inflammation, tachi-arrhythmias, and frailty in the social and community setting. Existing HF guidelines urge evaluation of depression in all HF patients, and numerous screening tools are available. Depression is ultimately diagnosed based on DSM-5 criteria. There are both non-pharmaceutical and pharmaceutical treatments for depression. Regarding depressed symptoms, non-pharmaceutical treatments, such as cognitive-behavioral therapy and physical exercise, have shown therapeutic results, under medical supervision and with an effort level adapted to the patient's physical resources, together with optimal HF treatment. In randomized clinical studies, selective serotonin reuptake inhibitors, the backbone of antidepressant treatment, did not demonstrate advantage over the placebo in patients with HF. New antidepressant medications are currently being studied and could provide a chance to enhance management, treatment, and control of depression in patients with HF. Conclusions: Despite the substantial link between depression and HF, their combination is underdiagnosed and undertreated. Considering the hopeful yet unclear findings of antidepressant trials, further research is required to identify people who may benefit from antidepressant medication. The goal of future research should be a complete approach to the care of these patients, who are anticipated to become a significant medical burden in the future.

Coronary Collateral Circulation: A New Predictor of Mortality in Heart Transplant Recipients With Allograft Vasculopathy

Coronary collateral arteries (CCAs) are anastomotic channels between vessels; although beneficial in atherosclerosis, their role in heart transplantation (HT) recipients is underinvestigated. CCAs initially develop as microcirculation and cardiac allograft vasculopathy (CAV), promoting immune-dependent proliferative angiogenic response, and play a role in their development. In our hypothesis, ischemia induced by coronary microvascular dysfunction (CMD) triggers the development of CCAs, which are, in turn, less functional as affected by CAV themselves.

Methods

One hundred twenty-one patients receiving HT at our institution were retrospectively evaluated and were included if transthoracic echocardiography with coronary flow velocity reserve (CFVR) assessment and coronary angiography were performed. CMD was defined as CFVR of ≤2.5. Patients with CAV were enrolled, and their angiograms were reviewed to evaluate the presence of CCAs. Cardiovascular mortality was assessed as the main clinical outcome.

Results

Forty patients were found to have CCAs. Patients with CCAs have lower CFVR than those without CCAs (2.22 ± 0.72 versus 2.69 ± 0.92;P = 0.003), reflecting in different rates of CMD in the 2 groups (72.5% versus 37%; P < 0.001). CMD is associated with higher CAV grades (P < 0.001), which are also associated with CCAs (P < 0.001). Patients with poorly developed CCAs have lower CFVR (P < 0.001). At multivariable analysis, CMD (P = 0.008) and higher CAV grades (P = 0.005) are independent predictors of CCAs. During the median follow-up time of 10.2 (6.6-13.3) y, patients with CCAs have been found to have higher mortality than those without CCAs (57.5% versus 32.1%; P = 0.007). CCAs are associated with a lower probability of survival also in patients with CMD (P < 0.001) and are independent predictors of mortality (P < 0.001).

Conclusions

Our results demonstrate an interplay between CAV, CMD, and CCAs. We confirm that CAV is associated with CMD, and we show, for the first time, that CMD is associated with CCAs. CCAs are pathophysiologically associated with more severe graft vasculopathy and independently predict mortality after HT.

Non-invasive coronary flow velocity reserve assessment predicts adverse outcome in women with unstable angina without obstructive coronary artery stenosis

Background

Evaluation of coronary flow velocity reserve (CFVR) is the physiological approach to assess the severity of coronary stenosis and microvascular dysfunction. Impaired CFVR occurs frequently in women with suspected or known coronary artery disease. The aim of this study was to assess the role of CFVR to predict long-term cardiovascular event rate in women with unstable angina (UA) without obstructive coronary artery stenosis.

Methods

CFVR in left anterior descending coronary artery was assessed by adenosine transthoracic echocardiograhy in 161 women admitted at our Department with UA and without obstructive coronary artery disease.

Results

During a mean FU of 32.5 ± 19.6 months, 53 cardiac events occurred: 6 nonfatal acute myocardial infarction, 22 UA, 7 coronary revascularization by percutaneous transluminal coronary angioplasty, 1 coronary bypass surgery, 3 ischemic stroke, and 8 episodes of congestive heart failure with preserved ejection fraction and 6 cardiac deaths. Using a ROC curve analysis, CFVR 2.14 was the best predictor of cardiac events and was considered as abnormal CFVR. Abnormal CFVR was associated with lower cardiac event-free survival (30 vs 80%, p < 0.0001). During FU, 70% of women with reduced CFVR had cardiac events whereas only 20% with normal CFVR (p = 0.0001). At multivariate Cox analysis, smoke habitus (p = 0.003), metabolic syndrome (p = 0.01), and CFVR (p < 0.0001) were significantly associated with cardiac events at FU.

Conclusion

Noninvasive CFVR provides an independent predictor of cardiovascular prognosis information in women with UA without obstructive coronary artery disease whereas, impaired CFVR seems to be associated with higher CV events at FU.

Coronary Flow Velocity Reserve by Echocardiography: Beyond Atherosclerotic Disease

Coronary flow velocity reserve (CFVR) is defined as the ratio between coronary flow velocity during maximal hyperemia and coronary flow at rest. Gold-standard techniques to measure CFVR are either invasive or require radiation and are therefore inappropriate for large-scale adoption. More than 30 years ago, echocardiography was demonstrated to be a reliable tool to assess CFVR, and its field of application rapidly expanded. Although initially validated to assess the hemodynamic relevance of a coronary stenosis, CFVR by echocardiography was later used to investigate coronary microcirculation. Microvascular dysfunction was detected in many different conditions, ranging from organ transplantation to inflammatory disorders and from metabolic diseases to cardiomyopathies. Moreover, it has been proven that CFVR by echocardiography not only detects coronary microvascular involvement but is also an effective prognostic factor that allows a precise risk stratification of the patients. In this review, we will summarize the many applications of CFVR by echocardiography, focusing on the coronary involvement of systemic diseases.

Coronary Flow Evaluation in Heart Transplant Patients Compared to Healthy Controls Documents the Superiority of Coronary Flow Velocity Reserve Companion as Diagnostic and Prognostic Tool

Background

Distinct contributions by functional or structural alterations of coronary microcirculation in heart transplantation (HT) and their prognostic role have not been fully elucidated. We aimed to identify the mechanisms of coronary microvascular dysfunction (CMD) in HT and their prognostic implications.

Methods

134 patients, surviving at least 5 years after HT, without evidence of angiographic vasculopathy or symptoms/signs of rejection were included. 50 healthy volunteers served as controls. All underwent the assessment of rest and hyperemic coronary diastolic peak flow velocity (DPVr and DPVh) and coronary flow velocity reserve (CFVR) and its inherent companion that is based on the adjusted quadratic mean: CCFVR = √{(DPVr)2 + (DPVh)2}. Additionally, basal and hyperemic coronary microvascular resistance (BMR and HMR) were estimated.

Results

Based on CFVR and DPVh, HT patients can be assigned to four endotypes: endotype 1, discordant with preserved CFVR (3.1 ± 0.4); endotype 2, concordant with preserved CFVR (3.4 ± 0.5); endotype 3, concordant with impaired CFVR (1.8 ± 0.3) and endotype 4, discordant with impaired CFVR (2.0 ± 0.2). Intriguingly, endotype 1 showed lower DPVr (p &lt; 0.0001) and lower DPVh (p &lt; 0.0001) than controls with lower CFVR (p &lt; 0.0001) and lower CCFVR (p &lt; 0.0001) than controls. Moreover, both BMR and HMR were higher in endotype 1 than in controls (p = 0.001 and p &lt; 0.0001, respectively), suggesting structural microvascular remodeling. Conversely, endotype 2 was comparable to controls. A 13/32 (41%) patients in endotype 1 died in a follow up of 28 years and mortality rate was comparable to endotype 3 (14/31, 45%). However, CCFVR was &lt; 80 cm/s in all 13 deaths of endotype 1 (characterized by preserved CFVR). At multivariable analysis, CMD, DPVh &lt; 75 cm/s and CCFVR &lt; 80 cm/s were independent predictors of mortality. The inclusion of CCFVR &lt; 80 cm/s to models with clinical indicators of mortality better predicted survival, compared to only adding CMD or DPVh &lt; 75 cm/s (p &lt; 0.0001 and p = 0.03, respectively).

Conclusion

A normal CFVR could hide detection of microvasculopathy with high flow resistance and low flow velocities at rest. This microvasculopathy seems to be secondary to factors unrelated to HT (less rejections and more often diabetes). The combined use of CFVR and CCFVR provides more complete clinical and prognostic information on coronary microvasculopathy in HT.

Non-Invasive Imaging in the Evaluation of Cardiac Allograft Vasculopathy in Heart Transplantation: A Systematic Review

Cardiac allograft vasculopathy (CAV) is the leading cause of long-term graft dysfunction in patients with heart transplantation and is linked with significant morbidity and mortality. Currently, the gold standard for diagnosing CAV is coronary imaging with intravascular ultrasound (IVUS) during traditional invasive coronary angiography (ICA). Invasive imaging, however, carries increased procedural risk and expense to patients in addition to requiring an experienced interventionalist. With the improvements in non-invasive cardiac imaging modalities such as transthoracic echocardiography (TTE), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), an alternative non-invasive imaging approach for the early detection of CAV may be feasible. In this systematic review, we explored the literature to investigate the utility of non-invasive imaging in diagnosis of CAV in >3000 patients across 49 studies. We also discuss the strengths and weaknesses for each imaging modality. Overall, all four imaging modalities show good to excellent accuracy for identifying CAV with significant variations across studies. Majority of the studies compared non-invasive imaging with ICA without intravascular imaging. In summary, non-invasive imaging modalities offer an alternative approach to invasive coronary imaging for CAV. Future studies should investigate longitudinal non-invasive protocols in low-risk patients after heart transplantation.

Imaging of Cardiac Transplantation: An Overview

Heart transplantation (HTx) remains the optimal treatment for selected patients with end-stage advanced heart failure. However, survival is limited early by acute rejection and long term by cardiac allograft vasculopathy (CAV). Even though the diagnosis of rejection is based on histology, cardiac imaging provides a pivotal role for early detection and severity assessment of these hazards. The present review focuses on the use and reliability of different invasive and non-invasive imaging modalities to detect and monitor CAV and rejection after HTx. Coronary angiography remains the corner stone in routine CAV surveillance. However, angiograms are invasive and underestimates the CAV severity especially in the early phase. Intravascular ultrasound and optical coherence tomography are invasive methods for intracoronary imaging that detects early CAV lesions not evident by angiograms. Non-invasive imaging can be divided into myocardial perfusion imaging, anatomical/structural imaging and myocardial functional imaging. The different non-invasive imaging modalities all provide clinical and prognostic information and may have a gatekeeper role for invasive monitoring. Acute rejection and CAV are still significant clinical problems after HTx. No imaging modality provides complete information on graft function, coronary anatomy and myocardial perfusion. However, a combination of invasive and non-invasive modalities at different stages following HTx should be considered for optimal personalized surveillance and risk stratification.

Invasive Assessment of Coronary Physiology Predicts Late Mortality After Heart Transplantation

BACKGROUND

The aim of this study is to determine the prognostic value of invasively assessing coronary physiology early after heart transplantation.

METHODS AND RESULTS

Seventy-four cardiac transplant recipients had fractional flow reserve, coronary flow reserve, index of microcirculatory resistance (IMR), and intravascular ultrasound performed down the left anterior descending coronary artery soon after (baseline) and 1 year after heart transplantation. The primary end point was the cumulative survival free of death or retransplantation at a mean follow-up of 4.5±3.5 years. The cumulative event-free survival was significantly lower in patients with a fractional flow reserve <0.90 at baseline (42% versus 79%; P=0.01) or an IMR ≥20 measured 1 year after heart transplantation (39% versus 69%; P=0.03). Patients in whom IMR decreased or did not change from baseline to 1 year had higher event-free survival compared with patients with an increase in IMR (66% versus 36%; P=0.03). Fractional flow reserve <0.90 at baseline (hazard ratio, 0.13; 95% confidence interval, 0.02-0.81; P=0.03), IMR ≥20 at 1 year (hazard ratio, 3.93; 95% confidence interval, 1.08-14.27; P=0.04), and rejection during the first year (hazard ratio, 6.00; 95% confidence interval, 1.56-23.09; P=0.009) were independent predictors of death/retransplantation, whereas intravascular ultrasound parameters were not.

CONCLUSIONS

Invasive measures of coronary physiology (fractional flow reserve and IMR) determined early after heart transplantation are significant predictors of late death or retransplantation.

Noninvasive Detection of Cardiac Allograft Vasculopathy by Stress Exercise Echocardiographic Assessment of Myocardial Deformation

BACKGROUND

The aim of this study was to evaluate the value of noninvasive assessment of cardiac allograft vasculopathy (CAV) in heart-transplanted patients by exercise stress myocardial deformation and coronary flow reserve (CFR) assessment.

METHODS

Fifty-eight heart-transplanted patients underwent semisupine exercise echocardiography with assessment of left ventricular (LV) longitudinal myocardial deformation. CAV was assessed by coronary angiography and noninvasive CFR by (15)O-H2O positron emission tomographic imaging and Doppler echocardiography. Patients were divided into three groups on the basis of angiographic CAV: no CAV (n = 21), mild CAV (n = 19), and severe CAV (n = 18).

RESULTS

Patients with severe CAV had significantly lower LV global longitudinal strain (GLS) at rest (no CAV, -16 ± 2%; mild CAV, -15 ± 2%; severe CAV, -12 ± 4%; P < .001), failed to increase LV GLS during exercise (no CAV, -5.7 ± 2.0%; mild CAV, -3.3 ± 2.9%; severe CAV, -0.2 ± 2.8%; P < .0001), and had significantly lower echocardiographic coronary flow velocity reserve (CFVR) (no CAV, 3.2 ± 0.4; mild CAV, 2.7 ± 0.7; severe CAV, 1.8 ± 0.5; P < .0001) and PET CFR (no CAV, 3.4 ± 0.9; mild CAV, 3.1 ± 0.9; severe CAV, 1.9 ± 0.8; P < .0001). Furthermore, patients with mild CAV had significantly lower exercise LV GLS and echocardiographic CFVR than patients with no CAV. Exercise LV GLS, echocardiographic CFVR, and PET CFR were significantly correlated with the presence of severe CAV in a logistic regression model (LV GLS odds ratio, 0.71; 95% CI, 0.60-0.84; P < .0001; echocardiographic CFVR odds ratio: 0.06; 95% CI, 0.01-0.23; PET CFR odds ratio, 0.17; 95% CI, 0.07-0.46). This relation remained significant after adjustment for symptoms and time since transplantation.

CONCLUSIONS

Noninvasive assessment of LV longitudinal myocardial deformation during exercise is feasible and strongly associated with the presence and degree of CAV. Exercise stress myocardial deformation analysis, echocardiographic CFVR, or PET CFR may serve as a noninvasive model for the detection of CAV.

Coronary microvascular dysfunction correlates with the new onset of cardiac allograft vasculopathy in heart transplant patients with normal coronary angiography

Coronary microvascular dysfunction is emerging as a strong predictor of outcome in heart transplantation (HT). We assessed the validity of microvascular dysfunction, defined by means of a reduced coronary flow reserve (CFR), as a factor associated with new onset epicardial cardiac allograft vasculopathy (CAV) or death. We studied 105 patients at 4 ± 1 years post-HT with a normal coronary angiography (CA). New onset CAV was assessed by CA. CFR was assessed in the left anterior descending (LAD) coronary artery by transthoracic Doppler echocardiography and calculated as the ratio of hyperaemic to basal blood flow velocity. A CFR ≤ 2.5 was considered abnormal. Epicardial CAV onset or death was assessed during a follow-up of 10 years. New onset CAV was diagnosed in 30 patients (28.6%) (Group A), and the CA was normal in the remaining 75 patients (71.4%) (Group B). Group A had reduced CFR compared with group B (2.4 ± 0.6 vs. 3.2 ± 0.7, p < 0.0001). A CFR ≤ 2.5 was independently associated with a higher probability of new onset CAV (p < 0.0001) and a higher probability of death, regardless of CAV onset (p < 0.01). Microvascular dysfunction is independently associated with the onset of epicardial CAV, and associated with a higher risk of death, regardless of CAV onset.

Coronary microvasculopathy in heart transplantation: Consequences and therapeutic implications

Despite the progress made in the prevention and treatment of rejection of the transplanted heart, cardiac allograft vasculopathy (CAV) remains the main cause of death in late survival transplanted patients. CAV consists of a progressive diffuse intimal hyperplasia and the proliferation of vascular smooth muscle cells, ending in wall thickening of epicardial vessels, intramyocardial arteries (50-20 μm), arterioles (20-10 μm), and capillaries (< 10 μm). The etiology of CAV remains unclear; both immunologic and non-immunologic mechanisms contribute to endothelial damage with a sustained inflammatory response. The immunological factors involved are Human Leukocyte Antigen compatibility between donor and recipient, alloreactive T cells and the humoral immune system. The non-immunological factors are older donor age, ischemia-reperfusion time, hyperlipidemia and CMV infections. Diagnostic techniques that are able to assess microvascular function are lacking. Intravascular ultrasound and fractional flow reserve, when performed during coronary angiography, are able to detect epicardial coronary artery disease but are not sensitive enough to assess microvascular changes. Some authors have proposed an index of microcirculatory resistance during maximal hyperemia, which is calculated by dividing pressure by flow (distal pressure multiplied by the hyperemic mean transit time). Non-invasive methods to assess coronary physiology are stress echocardiography, coronary flow reserve by transthoracic Doppler echocardiography, single photon emission computed tomography, and perfusion cardiac magnetic resonance. In this review, we intend to analyze the mechanisms, consequences and therapeutic implications of microvascular dysfunction, including an extended citation of relevant literature data.

Stress echo applications beyond coronary artery disease

Stress echocardiography is an established method for the diagnosis and prognostic stratification of coronary artery disease. In the last few years, the tremendous technological and conceptual versatility of this technique has been increasingly applied in challenging diagnostic fields. Today, in the echocardiography laboratory we can detect not only ischaemia from coronary artery stenosis, but can also recognize abnormalities of the coronary microvessels, myocardium, heart valves, pulmonary circulation, alveolar-capillary barrier, and right ventricle. Therefore, we evaluate coronary arteries as well as coronary microvascular disease (associated with diabetes and hypertension), suspected or overt dilated cardiomyopathy, systolic and diastolic heart failure, hypertrophic cardiomyopathy, athletes' hearts, valvular heart disease, congenital heart disease, incipient or overt pulmonary hypertension, and heart transplant patients for early detection of chronic or acute rejection as well as potential donors for better selection of suitable donor hearts. From a stress echo era with a one-fits-all approach (wall motion by 2D-echo in the patient with known or suspected coronary artery disease) now we have moved on to an omnivorous, next-generation laboratory employing a variety of technologies (from M-Mode to 2D and pulsed, continuous and colour Doppler, to lung ultrasound and real-time 3D echo, 2D speckle tracking and myocardial contrast echo) on patients covering the entire spectrum of severity (from elite athletes to patients with end-stage heart failure) and ages (from children with congenital heart disease to the elderly with low-flow, low-gradient aortic stenosis). For each patient, we can tailor a dedicated stress protocol with a specific method to address a particular diagnostic question. Provided that the acoustic window is acceptable and the necessary expertise available, stress echocardiography is useful and convenient in many situations, from valvular to congenital heart disease, and whenever there is a mismatch between symptoms during stress and findings at rest. Increasing societal concern regarding cost, environment and radiation risks of medical imaging will lead to a preferential application of ultrasound over competing techniques, due to its unsurpassed versatility, portability, absence of radiation, and low cost.

[Diagnosis, prevention and treatment of cardiac allograft vasculopathy]

The major limitation of long-term survival after cardiac transplantation is allograft vasculopathy, which consists of concentric and diffuse intimal hyperplasia. The disease still has a significant incidence, estimated at 30% five years after cardiac transplantation. It is a clinically silent disease and so diagnosis is a challenge. Coronary angiography supplemented by intravascular ultrasound is the most sensitive diagnostic method. However, new non-invasive diagnostic techniques are likely to be clinically relevant in the future. The earliest possible diagnosis is essential to prevent progression of the disease and to improve its prognosis. A new nomenclature for allograft vasculopathy has been published in July 2010, developed by the International Society for Heart and Lung Transplantation (ISHLT), establishing a standardized definition. Simultaneously, the ISHLT published new guidelines standardizing the diagnosis and management of cardiac transplant patients. This paper reviews contemporary concepts in the pathophysiology, diagnosis, prevention and treatment of allograft vasculopathy, highlighting areas that are the subject of ongoing research.

Clinical and functional correlates of early microvascular dysfunction after heart transplantation

BACKGROUND

Microvascular dysfunction is emerging as a strong predictor of outcome in heart transplant recipients. At this time, the determinants and consequences of early microvascular dysfunction are not well established. The objective of the study was to determine the risk factors and functional correlates associated with early microvascular dysfunction in heart transplant recipients.

METHODS AND RESULTS

Sixty-three heart transplant recipients who had coronary physiology assessment, right heart catheterization, and echocardiography performed at the time of their first annual evaluation were included in the study. Microvascular dysfunction was assessed using the recently described index of microcirculatory resistance. The presence of microvascular dysfunction, predefined by an index of microcirculatory resistance >20, was observed in 46% of patients at 1 year. A history of acute rejection and undersized donor hearts were associated with microvascular dysfunction at 1 year, with odds ratio of 4.0 (1.3-12.8) and 3.6 (1.2-11.1), respectively. Patients with microvascular dysfunction had lower cardiac index (3.1±0.7 versus 3.5±0.7 L/min per m(2); P=0.02) and mild graft dysfunction measured by echocardiography-derived left and right myocardial performance indices ([0.54±0.09 versus 0.43±0.09; P<0.01] and [0.47±0.14 versus 0.32±0.05; P<0.01], respectively). Microvascular dysfunction was also associated with a higher likelihood of death, graft failure, or allograft vasculopathy at 5 years after transplant (hazard ratio, 2.52 [95% CI, 1.04-5.91]).

CONCLUSIONS

A history of acute rejection during the first year and smaller donor hearts were identified as risk factors for early microvascular dysfunction. Microvascular dysfunction assessed using index of microcirculatory resistances at 1 year was also associated with worse graft function and possibly worse clinical outcomes.