Cardiac allograft vasculopathy coronary angiography

# Overview
Early diagnosis of cardiac allograft vasculopathy (CAV) is of utmost importance as it allows alterations to optimal immunosuppression and risk factor modification prolonging graft survival and reducing morbidity and mortality. In most transplant centers coronary angiography is currently used to screen and diagnose transplant associated coronary artery disease.

# Coronary Angiography
Previously, the diagnosis of CAV was made pathologically. However, with the advent of calcineurin-based immunosuppression post-cardiac transplant survival improved significantly and angiographic diagnosis became a standard. Currently, the International Society for Heart and Lung Transplantation (ISHLT) recommends annual invasive coronary angiography as the standard imaging technique to screen for CAV. Angiographic evidence of coronary artery disease is very common after heart transplantation. In a multiinstitutional study by Constanzo et al it was demonstrated that by the end of 5 years after transplantation 42% of heart transplant subjects had angiographic evidence of graft coronary artery disease.

## Coronary Artery Morphology in CAV
In contrast to native coronary artery disease where there is focal, eccentric narrowing of the coronary vessels, CAV involves a more diffuse process that manifests initially as intimal thickening followed later by concentric, longitudinal lesions. The earliest description of coronary artery morphology in CAV was given my Gao et al. According to the classification by Gao et al coronary lesions were classified as Type A, discrete stenosis, tubular stenosis, multiple stenoses in the proximal, middle and distal segments of coronary arteries; Type B, diffuse concentric narrowing of the coronary arteries with onset in the mid to distal segments; and Type C, diseased vessels, diffusely irregular with loss of small branches. However the nomenclature failed to provide prognostic significance of lesion classification. In 2010 the International Society for Heart and Lung Transplantation (ISHLT) proposed a standard nomenclature for CAV by integrating coronary angiographic findings with graft function and hemodynamics.
The ISHLT recommended standard nomenclature for CAV:
 A primary vessel denotes the proximal and middle 33% of the left anterior descending artery, the left circumflex, the ramus, and the dominant or codominant right coronary artery with the posterior descending and posterolateral branches. A secondary branch vessel includes the distal 33% of the primary vessels or any segment within a large septal perforator, diagonals, and obtuse marginal branches or any portion of a nondominant right coronary artery. Restrictive cardiac allograft physiology is defined as symptomatic heart failure with echocardiographic E to A velocity ratio of 2 (1.5 in children), shortened isovolumetric relaxation time (60 ms), shortened deceleration time (150 ms), or restrictive hemodynamic values (right atrial pressure 12 mm Hg, pulmonary capillary wedge pressure 25 mm Hg, cardiac index  2 l/min/m2). Adapted from the 2010 ISHLT consensus statement for recommended nomenclature of CAV

## Advantages
- Wide acceptability
- Reduced healthcare cost compared with other novel intracoronary imaging techniques
- Ease of performance

## Limitations
- Lower sensitivity compared with histopathological studies, intravascular ultrasound (IVUS) and optical coherence tomography (OCT), especially in detecting early-stage CAV Coronary angiography assesses only the arterial lumen but not the wall per se. Studies have demonstrated that early after heart transplantation disease pathology is confined to coronary arterial wall with minimal narrowing of the lumen. Therefore luminal assessment alone may lead to underestimation of the extent of disease pathology in early-CAV. In a 2006 study by Stork et al in 54 heart transplant recipients it was demonstrated that the positive predictive value of coronary angiography in detecting CAV was only 44% compared with IVUS.Similarly, using histologic correlations Johnson et al reported that lesions less than 25% stenosis were underestimated by coronary angiography. Also, positive remodeling that occurs early in the course of atherosclerosis and that is associated with plaque vulnerability is not detected by angiography.
- Risk of contrast nephropathy in heart transplant subjects in whom chronic renal failure is a usual comorbidity