Cardiovascular Magnetic Resonance in Right Heart and Pulmonary Circulation Disorders

Right heart and pulmonary circulation disorders are generally caused by right ventricle (RV) pressure overload, volume overload, and cardiomyopathy, and they are associated with distinct clinical courses and therapeutic approaches, although they often may coexist. Cardiac magnetic resonance (CMR) provides a noninvasive accurate and reproducible multiplanar anatomic and functional assessment, tissue characterization, and blood flow evaluation of the right heart and pulmonary circulation. This article reviews the current status of the CMR, the most recent techniques, the new parameters and their clinical utility in diagnosis, prognosis, and therapeutic management in the right heart and pulmonary circulation disorders.

Fate of moderate aortic regurgitation after cardiac surgery

OBJECTIVE

To determine the prevalence of concomitant aortic regurgitation (AR) in cardiac surgery and the outcomes of treatment options.

METHODS

Between April 2004 and June 2018, 3289 patients underwent coronary artery bypass, mitral valve, or aortic aneurysm surgery without aortic stenosis. AR was graded none/trivial (score = 0), mild (score = 1+), or moderate (score = 2+). Patients with untreated 2+ AR were compared with those with 0 or 1+ AR, and to those with 2+ AR who had aortic valve surgery. Thirty-day and late survival, echocardiography, and clinical outcomes were compared using propensity score matching.

RESULTS

One hundred thirty-eight patients (4.2%) had 2+ AR; and 45 (33%) received aortic valve repair (n = 9) or replacement (n = 36) in the treated group and were compared with 2765 untreated patients with 0 AR and 386 patients with 1+ AR. Valve surgery was more common with anatomic leaflet abnormalities: bicuspid aortic valve (9% vs 0%; P < .01), rheumatic valve disease (16% vs 3%; P < .01), and calcification (47% vs 27%; P = .021). In unadjusted analysis, lower preoperative AR grade was associated with increased 10-year survival (P < .001). At year 10, progression to more-than-moderate AR among moderate AR patients was 2.6% and late intervention rate was 3.1%. In the untreated 2+ AR group, on last follow-up echocardiogram, 58% had improvement in AR, 41% remained 2+, and only 1% progressed to severe AR.

CONCLUSIONS

Aortic valve surgery in select patients with concomitant moderate AR can be added with minimal added risk, but untreated AR does not influence long-term survival after cardiac surgery and rarely required late intervention.

The continuous heart failure spectrum: moving beyond an ejection fraction classification

Randomized clinical trials initially used heart failure (HF) patients with low left ventricular ejection fraction (LVEF) to select study populations with high risk to enhance statistical power. However, this use of LVEF in clinical trials has led to oversimplification of the scientific view of a complex syndrome. Descriptive terms such as 'HFrEF' (HF with reduced LVEF), 'HFpEF' (HF with preserved LVEF), and more recently 'HFmrEF' (HF with mid-range LVEF), assigned on arbitrary LVEF cut-off points, have gradually arisen as separate diseases, implying distinct pathophysiologies. In this article, based on pathophysiological reasoning, we challenge the paradigm of classifying HF according to LVEF. Instead, we propose that HF is a heterogeneous syndrome in which disease progression is associated with a dynamic evolution of functional and structural changes leading to unique disease trajectories creating a spectrum of phenotypes with overlapping and distinct characteristics. Moreover, we argue that by recognizing the spectral nature of the disease a novel stratification will arise from new technologies and scientific insights that will shape the design of future trials based on deeper understanding beyond the LVEF construct alone.

Relation of Late Gadolinium Enhancement and Extracellular Volume Fraction to Ventricular Arrhythmias in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HC) represents a major cause of sudden cardiac death in young adults. Late gadolinium enhancement (LGE) and extracellular volume (ECV) by T1 mapping are cardiac magnetic resonance (CMR) techniques to quantify fibrosis in HC. The relationships of LGE and ECV with ventricular arrhythmia, left ventricular (LV) diastolic function, and risk factors for sudden cardiac death (SCD) in HC are unclear. We studied 103 HC patients (mean age 51 ± 14, 42% women) who underwent CMR from 2012 to 2014. Global LGE and mean ECV were evaluated in relation to history of nonsustained ventricular tachycardia (NSVT), diastolic function by echocardiography, and SCD risk factors. LGE was present in 71 (69%) subjects. Wide variation was demonstrated in LGE (0.5% to 45.9%) and mean ECV (17.6% to 47.4%). Prevalence of NSVT increased continuously with LGE and was greater in subjects with ECV above the study population mean (27%). Increased LGE was associated with LV diastolic dysfunction and LV wall thickness. In conclusion, while ECV appears to have a threshold (27%) above which it is associated with NSVT, LGE demonstrates a more robust relationship with NSVT and measures of diastolic dysfunction.

Special Article - Acute myocardial injury in patients hospitalized with COVID-19 infection: A review

The Coronavirus Disease 2019 (COVID-19) is now a global pandemic with millions affected and millions more at risk for contracting the infection. The COVID-19 virus, SARS-CoV-2, affects multiple organ systems, especially the lungs and heart. Elevation of cardiac biomarkers, particularly high-sensitivity troponin and/or creatine kinase MB, is common in patients with COVID-19 infection. In our review of clinical analyses, we found that in 26 studies including 11,685 patients, the weighted pooled prevalence of acute myocardial injury was 20% (ranged from 5% to 38% depending on the criteria used). The plausible mechanisms of myocardial injury include, 1) hyperinflammation and cytokine storm mediated through pathologic T-cells and monocytes leading to myocarditis, 2) respiratory failure and hypoxemia resulting in damage to cardiac myocytes, 3) down regulation of ACE2 expression and subsequent protective signaling pathways in cardiac myocytes, 4) hypercoagulability and development of coronary microvascular thrombosis, 5) diffuse endothelial injury and 'endotheliitis' in several organs including the heart, and, 6) inflammation and/or stress causing coronary plaque rupture or supply-demand mismatch leading to myocardial ischemia/infarction. Cardiac biomarkers can be used to aid in diagnosis as well as risk stratification. In patients with elevated hs-troponin, clinical context is important and myocarditis as well as stress induced cardiomyopathy should be considered in the differential, along with type I and type II myocardial infarction. Irrespective of etiology, patients with acute myocardial injury should be prioritized for treatment. Clinical decisions including interventions should be individualized and carefully tailored after thorough review of risks/benefits. Given the complex interplay of SARS-CoV-2 with the cardiovascular system, further investigation into potential mechanisms is needed to guide effective therapies. Randomized trials are urgently needed to investigate treatment modalities to reduce the incidence and mortality associated with COVID-19 related acute myocardial injury.

State of the Art: Imaging for Myocardial Viability: A Scientific Statement From the American Heart Association

A substantial proportion of patients with acute myocardial infarction develop clinical heart failure, which remains a common and major healthcare burden. It has been shown that in patients with chronic coronary artery disease, ischemic episodes lead to a global pattern of cardiomyocyte remodeling and dedifferentiation, hallmarked by myolysis, glycogen accumulation, and alteration of structural proteins. These changes, in conjunction with an impaired global coronary reserve, may eventually become irreversible and result in ischemic cardiomyopathy. Moreover, noninvasive imaging of myocardial scar and hibernation can inform the risk of sudden cardiac death. Therefore, it would be intuitive that imaging of myocardial viability is an essential tool for the proper use of invasive treatment strategies and patient prognostication. However, this notion has been challenged by large-scale clinical trials demonstrating that, in the modern era of improved guideline-directed medical therapies, imaging of myocardial viability failed to deliver effective guidance of coronary bypass surgery to a reduction of adverse cardiac outcomes. In addition, current available imaging technologies in this regard are numerous, and they target diverse surrogates of structural or tissue substrates of myocardial viability. In this document, we examine these issues in the current clinical context, collect current evidence of imaging technology by modality, and inform future directions.

Percutaneous or surgical revascularization is associated with survival benefit in stable coronary artery disease

Aims 

We assessed the association between early invasive therapy, burden of ischaemia, and survival benefit separately for percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). Ischaemia involving more than 10% of the left ventricular myocardium may identify patients who benefit from revascularization. However, it is not clear whether this association exists with both PCI and CABG.

Materials and results

Patients who underwent single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) between 1992 and 2012 were identified. Early revascularization was defined as PCI or CABG performed within 90 days of SPECT MPI. The association between early PCI or CABG and all-cause mortality was assessed using a doubly robust, propensity score matching analysis. In total, 54 522 patients were identified, with median follow-up 8.0 years. Early PCI was performed in 2688 patients and early CABG in 1228. In the matched cohorts, early revascularization was associated with improved survival compared to medical therapy in patients with more than 15% ischaemia for both PCI [adjusted hazard ratio (HR) 0.70, P = 0.002] and CABG (adjusted HR 0.73, P = 0.008).

Conclusion 

In this observational analysis, both PCI and CABG were associated with reduced all-cause mortality in the presence of moderate to severe ischaemia after adjusting for factors leading to revascularization. As the threshold for improved outcomes with revascularization was similar for PCI and CABG, our results suggest that decisions for PCI vs. CABG for early revascularization should be determined by coronary anatomy, patient characteristics, and shared decision making, but not by the burden of ischaemia.

Myocardial ischemia: From disease to syndrome

Although current guidelines on the management of stable coronary artery disease acknowledge that multiple mechanisms may precipitate myocardial ischemia, recommended diagnostic, prognostic and therapeutic algorithms are still focused on obstructive epicardial atherosclerotic lesions, and little progress has been made in identifying management strategies for non-atherosclerotic causes of myocardial ischemia. The purpose of this consensus paper is three-fold: 1) to marshal scientific evidence that obstructive atherosclerosis can co-exist with other mechanisms of ischemic heart disease (IHD); 2) to explore how the awareness of multiple precipitating mechanisms could impact on pre-test probability, provocative test results and treatment strategies; and 3) to stimulate a more comprehensive approach to chronic myocardial ischemic syndromes, consistent with the new understanding of this condition.

Hypertrophic Cardiomyopathy Is Associated with Altered Left Ventricular 3D Blood Flow Dynamics

Purpose

To employ four-dimensional (4D) flow MRI to investigate associations between hemodynamic parameters with systolic anterior motion (SAM), mitral regurgitation (MR), stroke volume, and cardiac mass in patients with hypertrophic cardiomyopathy (HCM).

Materials and Methods

A total of 13 patients with HCM (51 years ± 16 [standard deviation]; 10 men) and 11 age-matched healthy control subjects (54 years ± 15; eight men) underwent cardiac 4D flow MRI data analysis including calculation of peak systolic and diastolic control-averaged left ventricular (LV) velocity maps to quantify volumes of elevated velocity (EVV) in the left ventricle. Standard-of-care cine imaging was performed in short-axis, LV outflow tract (LVOT), and two-, three-, and four-chamber views on which the presence of SAM, presence of MR, total stroke volume, and cardiac mass were assessed.

Results

Systolic EVV in patients with HCM was 7 mL ± 5, which was significantly associated with elevated aortic peak velocity (R = 0.87; P < .001), decreased LVOT diameter (R = 0.68; P = .01), and increased cardiac mass (R = 0.62; P = .02). In addition, EVV differed significantly between patients with and those without SAM (10 mL ± 4.7 vs 3 mL ± 2.3; P = .03) and those with and those without MR (9.9 mL ± 4.8 vs 4.0 mL ± 3.2; P < .05). In the atrial systolic phase, peak diastolic velocity in the LV correlated with septal thickness (R = 0.66; P = .01).

Conclusion

Quantification and visualization of EVV in the LV is feasible and may provide further insight into the clinical manifestations of altered hemodynamics in HCM.© RSNA, 2020.