Microvasculopathy Observed in Early or Late Endomyocardial Biopsies Is Not Related to Angiographically Confirmed Transplanted Heart Coronary Vasculopathy

Increased fibrosis and microvessel disease in allograft endomyocardial biopsies of children with chronic graft failure due to cardiac allograft vasculopathy

INTRODUCTION

Chronic graft failure (CGF) is the leading cause of mortality in pediatric heart transplant (PHT) patients and has multifactorial pathogenesis including cardiac allograft vasculopathy (CAV). CGF can present with microvessel disease (MVD) and myocardial fibrosis on endomyocardial biopsies (EMB). We investigated if CGF due to moderate- severe (M-S) CAV has histopathologic MVD and fibrosis prior to or at the time of CAV diagnosis.

METHOD

This retrospective case-control study included PHT with CGF secondary to M-S CAV. Control patients had no CAV or CGF. EMBs from CAV (3 sets: at 1-year post-transplant 1yrCAV, pre-CAV, and at the time of CAV diagnosis) and non-CAV cohorts were reviewed to grade the fibrosis and quantify MVD. Histopathologic changes were correlated and compared between CAV/non-CAV groups.

RESULTS

Each group had 8 patients. The median age at transplantation and time since transplant were similar between the two groups (P=.71 and P=.91, respectively). Fibrosis grade was 3.0 for CAV cohort compared to 1.0 for control (P= .003) and MVD score was 2.1 in CAV and 0.5 in non-CAV patients (P=.003). Similar degrees of fibrosis and MVD were present even before any evidence of CAV (1yrCAV fibrosis grade 2.5, pre-CAV fibrosis grade 2; 1yrCAV vs CAV P=.75, pre-CAV vs CAV P=.63; 1yrCAV MVD score 2, pre-CAV MVD score 2; 1yrCAV vs CAV P=1, pre-CAV vs CAV P=.91). The degree of MVD correlated with fibrosis (r=0.63, P<.0001) for all EMBs.

CONCLUSION

Simultaneous myocardial fibrosis and MVD are noted in CGF secondary to M-S CAV, changes that occur before angiographic CAV. EMBs can reveal significant changes in patients with subsequent development of CAV and may be used to modify the follow-up and treatment for these high-risk patients.

Myocardial Vascular Function Assessed by Dynamic Oxygenation-sensitive Cardiac Magnetic Resonance Imaging Long-term Following Cardiac Transplantation

BACKGROUND

Coronary vascular function is related to adverse outcomes following cardiac transplantation (CTx) in patients with or without cardiac allograft vasculopathy (CAV). The noninvasive assessment of the myocardial vascular response using oxygenation-sensitive cardiac magnetic resonance (OS-CMR has not been investigated in stable long-term CTx recipients).

METHODS

CTx patients were prospectively recruited to complete a CMR study with a breathing maneuver of hyperventilation followed by a voluntary apnea. Changes in OS-sensitive signal intensity reflecting the myocardial oxygenation response were monitored and expressed as % change in response to these breathing maneuvers. Myocardial injury was further investigated with T2-weighted imaging, native and postcontrast T1 measurements, extracellular volume measurements, and late gadolinium enhancement.

RESULTS

Forty-six CTx patients with (n = 23) and without (n = 23) CAV, along with 25 healthy controls (HC), were enrolled. The OS response was significantly attenuated in CTx compared with HC at the 30-second time-point into the breath-hold (2.63% ± 4.16% versus 6.40% ± 5.96%; P = 0.010). Compared with HC, OS response was lower in CTx without CAV (2.62% ± 4.60%; P < 0.05), while this response was further attenuated in patients with severe CAV (grades 2-3, -2.24% ± 3.65%). An inverse correlation was observed between OS-CMR, ventricular volumes, and diffuse fibrosis measured by extracellular volume mapping.

CONCLUSIONS

In heart transplant patients, myocardial oxygenation is impaired even in the absence of CAV suggesting microvascular dysfunction. These abnormalities can be identified by oxygenation-sensitive CMR using simple breathing maneuvers.

Cardiac allograft vasculopathy: diagnosis, therapy, and prognosis

Development of cardiac allograft vasculopathy represents the major determinant of long-term survival in patients after heart transplantation. Due to graft denervation, these patients seldom present with classic symptoms of angina pectoris, and the first clinical presentations are progressive heart failure or sudden cardiac death. Although coronary angiography remains the routine technique for coronary artery disease detection, it is not sensitive enough for screening purposes. This is especially the case in the first year after transplantation when diffuse and concentric vascular changes can be easily detected only by intravascular ultrasound. The treatment of the established vasculopathy is disappointing, so the primary effort should be directed toward early prevention and diagnosis. Due to diffuse vascular changes, revascularization procedures are restricted only to a relatively small proportion of patients with favorable coronary anatomy. Percutaneous coronary intervention is preferred over surgical revascularization since it leads to better acute results and patient survival. Although there is no proven long-term advantage of drug-eluting stents for the treatment of in-stent restenosis, they are preferred over bare-metal stents. Severe vasculopathy has a poor prognosis and the only definitive treatment is retransplantation. This article reviews the present knowledge on the pathogenesis, diagnosis, treatment, and prognosis of cardiac allograft vasculopathy.