Right ventricular mechanics and exercise capacity in patients with microvascular angina: The impact of microvascular function

Right Ventricular Function and Exercise Tolerance in Patients with ST-Elevation Myocardial Infarction

BACKGROUND

Following ST-segment elevation myocardial infarction (STEMI), patients with cardiac dysfunction have limitations in performing physical activity. Right ventricular (RV) function is a determinant in improving functional capacity, and cardiac rehabilitation (CR) is essential for this patient cohort.

OBJECTIVE

To evaluate the association of RV function with exercise tolerance after a CR program in patients with STEMI.

METHODS

Retrospective cohort study in patients with STEMI from January to December 2019. They underwent an echocardiographic assessment of RV function before a 16-session CR program. A cardiopulmonary exercise (CPX) testing was performed before and after the CR program. We analyzed whether RV function measured before CR was significantly associated with exercise tolerance before and after the CR program and the degree of improvement. Comorbidity, demographic and anatomic variables were documented. A p-value < 0.05 was considered statistically significant.

RESULTS

A total of 109 patients were included. Of all, 3.7% had global RV dysfunction, 10.1% had radial RV dysfunction, and 11% had longitudinal RV dysfunction. An association between radial or longitudinal RV dysfunction and the absence of improvement in cardiorespiratory fitness (> 1 peak VO2equivalents) was observed (p = 0.028, p = 0.008, respectively). A significant correlation was observed between longitudinal RV dysfunction with initial peak VO2equivalents (pVO2eq) (p = 0.046), final pVO2eq (p = 0.003), and difference in pVO2eq (p = 0.009). A correlation was also identified between global RV dysfunction and the initial pVO2eq (p = 0.045), final pVO2eq (p = 0.012), and difference in pVO2eq (p = 0.032).

CONCLUSIONS

RV dysfunction is associated with a lower capacity to exercise; CR programs can be extended or modified in these patients.

Echocardiographic assessment of primary microvascular angina and primary coronary microvascular dysfunction

There is an increasing interest in the role of echocardiography in the evaluation of primary microvascular angina, which is attributed to primary coronary microvascular dysfunction. Valid echocardiographic techniques are expected to facilitate the diagnosis and follow-up of these patients and would be valuable for research purposes and therapy evaluation. However, adequate echocardiographic data are lacking, and the interpretation of the limited available literature is hindered by the previous addition of microvascular angina under more inclusive entities, such as cardiac syndrome X. In experienced hands, the assessment of primary coronary microvascular dysfunction in patients with suspected primary microvascular angina, using multiple echocardiographic techniques is feasible, relatively inexpensive, and safe. Exclusion of obstructive epicardial coronary artery disease is, however, a prerequisite for diagnosis. Two-dimensional transthoracic echocardiography, routine stress echocardiography, and speckle-tracking echocardiography indirectly assess primary coronary microvascular dysfunction by evaluating potential impairment in myocardial function and lack diagnostic sensitivity and specificity. Conversely, certain echocardiographic techniques, including Doppler-derived coronary flow velocity reserve and myocardial contrast echocardiography, assess some coronary microvascular dysfunction parameters and have exhibited diagnostic and prognostic potentials. Doppler-derived coronary flow velocity reserve is the best studied and only guideline-approved echocardiographic technique for documenting coronary microvascular dysfunction in patients with suspected microvascular angina. Myocardial contrast echocardiography, by comparison, can detect heterogeneous and patchy myocardial involvement by coronary microvascular dysfunction, which is an advantage over the common practice of coronary flow velocity reserve assessment in a single vessel (commonly the left anterior descending artery) which only reflects regional microvascular function. However, there is no consensus regarding the diagnostic criteria, and expertise performing this technique is limited. Echocardiography remains underexplored and inadequately utilized in the setting of microvascular angina and coronary microvascular dysfunction. Appraisal of the current echocardiographic literature regarding coronary microvascular dysfunction and microvascular angina is important to stay current with the progress in its clinical recognition and create a basis for future research and technological advancements.

Parameter subset reduction for patient-specific modelling of arrhythmogenic cardiomyopathy-related mutation carriers in the CircAdapt model

Arrhythmogenic cardiomyopathy (AC) is an inherited cardiac disease, clinically characterized by life-threatening ventricular arrhythmias and progressive cardiac dysfunction. Patient-specific computational models could help understand the disease progression and may help in clinical decision-making. We propose an inverse modelling approach using the CircAdapt model to estimate patient-specific regional abnormalities in tissue properties in AC subjects. However, the number of parameters (n = 110) and their complex interactions make personalized parameter estimation challenging. The goal of this study is to develop a framework for parameter reduction and estimation combining Morris screening, quasi-Monte Carlo (qMC) simulations and particle swarm optimization (PSO). This framework identifies the best subset of tissue properties based on clinical measurements allowing patient-specific identification of right ventricular tissue abnormalities. We applied this framework on 15 AC genotype-positive subjects with varying degrees of myocardial disease. Cohort studies have shown that atypical regional right ventricular (RV) deformation patterns reveal an early-stage AC disease. The CircAdapt model of cardiovascular mechanics and haemodynamics has already demonstrated its ability to capture typical deformation patterns of AC subjects. We, therefore, use clinically measured cardiac deformation patterns to estimate model parameters describing myocardial disease substrates underlying these AC-related RV deformation abnormalities. Morris screening reduced the subset to 48 parameters. qMC and PSO further reduced the subset to a final selection of 16 parameters, including regional tissue contractility, passive stiffness, activation delay and wall reference area. This article is part of the theme issue 'Uncertainty quantification in cardiac and cardiovascular modelling and simulation'.