CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 3, July/August 2023 138 AFRICA Regarding non-ischaemic cardiomyopathy, Ge et al.14 investigated whether structural abnormality on CMR represented by LGE may be a predictor of MACE in patients with non-sustained ventricular tachycardia (NSVT) and ventricular tachycardia (VT)/SCD. They studied 651 patients (age 54 ± 15; 61% male) referred to CMR for ventricular arrhythmia, who were divided into two groups according to the presence of NSVT (53%) or sustained VT/aborted SCD (47%). MACE was a composite of cardiovascular death, a need for heart transplantation or left ventricular assist device and recurrent VT/ventricular fibrillation needing therapy. The mean LVEF was 54 ± 13% and LGE was present in 39% of patients (mean 9.5 ± 8%).14 A structurally abnormal heart, defined by LGE, abnormalities in wall motion or impaired systolic function was observed in 52% of patients (n = 336). A change in diagnostic impression based on CMR took place for 27% of patients with NSVT versus 40% of patients with VT/SCD (p < 0.001). A total of 122 patients experienced MACE during the follow-up period (median, 3.6 years). Structural abnormality detected on CMR was found to be an independent predictor of MACE (HR 3.65; 95% CI: 2.09–6.27; p < 0.001).14 Although each of the three methods used to quantify the myocardial scar using LGE in CMR has a different concept to calculate the size of the scar, they all showed comparable results. The manual method is a commonly used technique,15 however, it is extremely time consuming. The second method, using the total number of segments involving any LGE is theoretically less accurate as it considers one segment affected even if the late enhancement is focal or minimal. On the other hand, it is the least time-consuming method as it gives only a general impression of how many of the myocardial segments include scarred tissue. However, the third method, summation of the percentage of the scarred myocardium in each segment of the 17 myocardial segments, is less time consuming than the manual one, with considerable accuracy in representing how much of the myocardium is unhealthy. Many other methods were tested and compared for accuracy in quantifying myocardial scar. Flett et al.15 studied the reproducibility of LGE quantification techniques in three different pathological conditions: acute myocardial infarction, chronic myocardial infarction and HCM, using seven techniques. These were manual quantification, automatic methods including thresholding by 2-, 3-, 4-, 5- or 6-SD above remote myocardium, and the FWHM technique. They concluded that regardless of the underlying disease, the FWHM technique for LGE quantification gave mean LGE volume results similar to manual quantification and it was statistically the most reproducible, reducing the required sample sizes by up to a half.15 Another study by Gao et al.16 using automatic thresholding measured a 50% larger scar size going from 5-SD to 2-SD thresholds above remote myocardial signal intensity. Neilan et al.9 found that scar size was, on average, 50% greater using the 2-SD technique versus the FWHM technique (9 ± 5% by 2-SD method vs 6 ± 4% by FWHM method), however, there was close correlation between both the measurements (r = 0.92, p < 0.001), and more importantly, both methods of quantification showed robust prognostic association. Therefore, despite the different ways used to quantify myocardial scar, manual assessment is considered one of the most accurate methods. However, no one specific method has been agreed on to be the standard yet. The small number of patients included in our study, especially in each type of cardiomyopathy, is one of the limitations in our study. In addition, longer follow-up time would have added more significant predictive value. Conclusion Myocardial scar/fibrosis using CMR is a reliable parameter that can reflect the degree of diseased myocardium. The amount of scarred or fibrosed myocardium is found to be directly linked to the severity of the clinical event in both ICM and NCIM patients. The larger the scar size, the more severe was the clinical event, even with preserved LVEF. Therefore, quantification of myocardial scar/fibrosis could be used as a predictor for cardiac events, hospitalisation and SCD. LVEF is not always linked with severity of the cardiac event, especially in NICM patients. Low LVEF was mainly linked with hospitalisation in both ICM and NICM patients. References 1. ECG & Echo Learning. Clinical Echocardiography. Myocardial mechanics: structure and function of myocardial fibers. Available from: https:// ecgwaves.com/topic/structure-and-function-of-myocardial-fibersmyocardium/ 2. Treibel TA, White SK, Moon JC. Myocardial tissue characterization: histological and pathophysiological correlation. Curr Cardiovasc Imaging Rep 2014; 7(3): 9254. 3. Klein C, Nekolla SG, Balbach T, Schnackenburg B, Nagel E, Fleck E, et al. The influence of myocardial blood flow and volume of distribution on late Gd-DTPA kinetics in ischemic heart failure. J Magn Reson Imaging 2004; 20(4): 588–593. 4. Klein C, Schmal TR, Nekolla SG, Schnackenburg B, Fleck E, Nagel E. Mechanism of late gadolinium enhancement in patients with acute myocardial infarction. J Cardiovasc Magn Reson 2007; 9(4): 653–658. 5. Kelle S, Roes SD, Klein C, Kokocinski T, de Roos A, Fleck E, et al. Prognostic value of myocardial infarct size and contractile reserve using magnetic resonance imaging. J Am Coll Cardiol 2009; 54(19): 1770–1777. 6. Beek AM, Kühl HP, Bondarenko O, Twisk JW, Hofman MB, van Dockum WG, et al. Delayed contrast-enhanced magnetic resonance imaging for the prediction of regional functional improvement after acute myocardial infarction. J Am Coll Cardiol 2003; 42 (5): 895–901. 7. McCrohon JA, Moon JC, Prasad SK, McKenna WJ, Lorenz CH, Coats AJ, et al. Differentiation of heart failure related to dilated cardiomyopathy and coronary artery disease using gadolinium-enhanced cardiovascular magnetic resonance. Circulation 2003; 108(1): 54–59. 8. Kim RJ, Fieno DS, Parrish TB, Harris K, Chen EL, Simonetti O, et al. Relationship of MRI delayed contrast enhancement to irreversible injury, infarct age, and contractile function. Circulation 1999; 100(19): 1992–2002. 9. Neilan TG, Coelho-Filho OR, Danik SB, Shah RV, Dodson JA, Verdini DJ, et al. CMR quantification of myocardial scar provides additive prognostic information in nonischemic cardiomyopathy. J Am Coll Cardiol Cardiovasc Imaging 2013; 6(9): 944–954. 10. Gulati A, Jabbour A, Ismail TF, Guha K, Khwaja J, Raza S, et al. Association of fibrosis with mortality and sudden cardiac death in patients with nonischemic dilated cardiomyopathy. J Am Med Assoc
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