Medial-ABC: an algorithm for the correspondence between myocardium and coronary artery mesh models based on the medial axis of coronary artery

The role of coronary arteries is to supply sufficient blood to myocardium. Obstruction of coronary arteries limits blood supply and causes myocardial ischemia or acute myocardial infarction, a major cause of human death. Hence, the quantification of the regional amount of heart muscle subtended by obstructed coronary arteries is of critical value in clinical medicine. However, conventional methods are inaccurate and frequently disagree with clinical practice. This study proposes a novel medial-axis-based correspondence (Medial-ABC) algorithm to find the correspondence between myocardium and coronary artery in order to segment regional myocardium at risk subtended by any potentially obstructed coronary artery. Given the triangular mesh models of coronary artery and myocardium, the proposed algorithm (i) computes the medial axis of coronary artery, (ii) finds the correspondence using the medial axis of coronary artery, and (iii) segments the coronary artery and myocardium. The proposed algorithm provides a robust mathematical linkage between myocardium at risk and supplying coronary arteries so that ischemic myocardial regions can be accurately identified. Hence, both the extent and severity of myocardial ischemia can be quantified effectively, efficiently, and accurately. Furthermore, the constructed mesh model of segmented coronary artery and myocardium can be post-processed for applications such as building optimization models of cardiac systems. The CardiacVis program, which implements the Medial-ABC algorithm, is freely available at Voronoi Diagram Research Center (http://voronoi.hanyang.ac.kr/software/cardiacvis) and will be an invaluable tool for quantitative patient-specific risk stratification in clinical practice.

Myocardial bridging in the era of a drug epidemic: a case report addressing the need to revisit donor organ assessment

Background Myocardial bridging (MB), though typically a benign finding, may occasionally lead to syncope, myocardial infarction, arrhythmia, or sudden death. Surgical denervation of transplanted hearts complicates the management of such incidentally detected post-transplant coronary anomalies due to the lack of classic ischaemic symptoms. Case summary A middle-aged female underwent an uncomplicated cardiac transplantation from a healthy male donor in his early 20s who had suffered a cardiac arrest while using cocaine. Given the young donor age, a pre-transplant coronary angiogram (CAG) was deferred. However, 6-week post-transplant, routine CAG, and intravascular ultrasound revealed an extensive MB spanning a significant portion of the left anterior descending coronary artery with substantial myocardium at risk. A stress test with myocardial perfusion imaging performed to evaluate the functional significance of the bridge did not reveal any perfusion abnormalities in the myocardium at risk. Discussion In current practice, younger donors often do not undergo pre-transplantation CAG routinely performed in older donors given the lower prevalence of significant coronary disease. However, post-operatively this young donor was found to have passed on a potentially life-threatening MB to a denervated recipient, who cannot manifest typical anginal symptoms during ischaemia, thereby challenging providers to choose among strategies of watchful waiting, risk stratification, or pre-emptive intervention. In retrospect, the donor’s mode of death may have signalled an underlying structural abnormality that warranted further pre-transplant characterization. In order to ensure optimal quality of transplanted hearts, young donors may warrant pre-transplant CAG despite their age, particularly those with a history of drug use or suspicious mode of death.

Cardioprotection during ischemia by coronary collateral growth

Ischemic heart diseases (IHD) cause millions of deaths around the world annually. While surgical and pharmacological interventions are commonly used to treat patients with IHD, their efficacy varies from patient to patient and is limited by the severity of the disease. One promising, at least theoretically, approach for treating IHD is induction of coronary collateral growth (CCG). Coronary collaterals are arteriole-to-arteriole anastomoses that can undergo expansion and remodeling in the setting of coronary disease when the disease elicits myocardial ischemia and creates a pressure difference across the collateral vessel that creates unidirectional flow. Well-developed collaterals can restore blood flow in the ischemic area of the myocardium and protect the myocardium at risk. Moreover, such collaterals are correlated to reduced mortality and infarct size and better cardiac function during occlusion of coronary arteries. Therefore, understanding the process of CCG is highly important as a potentially viable treatment of IHD. While there are several excellent review articles on this topic, this review will provide a unified overview of the various aspects related to CCG as well as an update of the advancements in the field. We also call for more detailed studies with an interdisciplinary approach to advance our knowledge of CCG. In this review, we will describe growth of coronary collaterals, the various factors that contribute to CCG, animal models used to study CCG, and the cardioprotective effects of coronary collaterals during ischemia. We will also discuss the impairment of CCG in metabolic syndrome and the therapeutic potentials of CCG in IHD.

Diagnostic Accuracy Of The Electrocardiographic Decision Support – Myocardial Ischaemia (EDS-MI) Algorithm In Detection Of Acute Coronary Occlusion

Electrocardiographic Decision Support – Myocardial Ischaemia (EDS-MI) is a graphical decision support for detection and localization of acute transmural ischaemia. A recent study indicated that EDS-MI performs well for detection of acute transmural ischaemia. However, its performance has not been tested in patients with non-ischaemic ST-deviation. We aimed to optimize the diagnostic accuracy of EDS-MI in patients with verified acute coronary occlusion as well as patients with non-ischaemic ST deviation and compare its performance with STEMI criteria. We studied 135 patients with non-ischaemic ST deviation (perimyocarditis, left ventricular hypertrophy, takotsubo cardiomyopathy and early repolarization) and 117 patients with acute coronary occlusion. In 63 ischaemic patients, the extent and location of the ischaemic area (myocardium at risk) was assessed by both cardiovascular magnetic resonance imaging and EDS-MI. Sensitivity and specificity of ST elevation myocardial infarction criteria were 85% (95% confidence interval (CI) 77, 90) and 44% (95% CI 36, 53) respectively. Using EDS-MI, sensitivity and specificity increased to 92% (95% CI 85, 95) and 81% (95% CI 74, 87) respectively (p=0.035 and p<0.001). Agreement was strong (83%) between cardiovascular magnetic resonance imaging and EDS-MI in localization of ischaemia. Mean myocardium at risk was 32% (± 10) by cardiovascular magnetic resonance imaging and 33% (± 11) by EDS-MI when the estimated infarcted area according to Selvester QRS scoring was included in myocardium at risk estimation. In conclusion, EDS-MI increases diagnostic accuracy and may serve as an automatic decision support in the early management of patients with suspected acute coronary syndrome. The added clinical benefit in a non-selected clinical chest pain population needs to be assessed.