How can we sort out our patients before sending them to the cardiac magnetic resonance laboratories?

This editorial refers to ‘Electrocardiographic predictors of left ventricular scar in athletes with right bundle branch block premature ventricular beats’, by L. Sciarra et al., https://doi.org/10.1093/eurjpc/zwae010. We know that regular physical activity (PA) and improved cardiometabolic fitness (CRF) reduce the incidence of all-cause and cardiovascular mortality. For example, each metabolic equivalent increase of CRF has been shown to be associated with a 25% point reduction in overall mortality in patients with coronary artery disease.1 We now have ample evidence that backs the benefits of exercise and PA for our quality of life, cardiovascular health, and longevity. Therefore, exercise and PA have now become one of the most powerful tools for the prevention and treatment of cardiovascular diseases (CVDs). This is why we, cardiologists, recommend daily exercise to our patients. However, we also know harmful effects of exercise, including sports-related acute and chronic injuries, heat stroke, and most tragically, sudden cardiac arrest and death (SCA/D). A recent report from France comprising 1 073 772 runners has reported an incidence of long-distance race-related SCA to be 1.67 per 100 000.2 Peterson and coauthors3 also have reported that annual incidence rate of SCA/D among high school and National Collegiate Athletic Association athletes was 1:65 872 and 1:50 768 athletes per year, respectively. Various cardiac conditions, e.g. ischaemic heart diseases, congenital coronary artery abnormalities, channelopathies, valvular heart diseases, and commotio cordis, give rise to ventricular tachycardia (VT) and subsequent ventricular fibrillation (Vf) and SCA/D in athletes. When we encounter ventricular arrhythmias (VAs) in athletes, the first thing we distinguish would be whether they are polymorphic or monomorphic. Polymorphic VAs are considered basically malignant and often degenerate to Vf and subsequent SCA. Ventricular arrhythmias of this type in the young are most often observed in patients with channelopathies such as long QT syndrome and Brugada syndrome. These channelopathies usually show characteristic electrocardiographic findings, which leads us to consider further advanced clinical testing and implantable cardioverter defibrillators for the prevention of SCD. On the other hand, we know monomorphic VAs among athletes are rather benign. A recent report by Havakuk et al.4 shows that most patients with monomorphic sustained VT do not even complain palpitations. However, we have gaining evidence that re-entrant (basically monomorphic) VAs associated with ventricular scar (VS) can provoke life-threatening VT/Vf.5–13 Although VS is observed most often in patients with ischaemic heart diseases, non-ischaemic ventricular scar (NVS) has recently been identified as an important substrate for sustained VT/Vf in athletes.9,12 Also, a study by di Gioia et al.12 has reported it to be a common cause of SCD related to sport. Non-ischaemic ventricular scar is most often observed among patients with various cardiomyopathies including hypertrophic, dilated, and arrhythmogenic cardiomyopathies (ACMs).10,11,13 However, NVS is sometimes found in highly trained athletes. Venlet et al.14 have reported two types of VS among athletes, one localized in the sub-epicardium of the right ventricular outflow tract (RVOT), another wider around the tricuspid annulus. Athletes affected by the RVOT scar had harder and longer history of training, whose VT are characterized by shorter cycle length and better response to ablation and lack of degenerating into Vf.14 The peritricuspid scar has a lot of similarities with that observed in patients with hereditary right dominant ACM and thus can be a cause of SCA/D. However, as Sawant et al.15 have reported that athletes with complex VA have an incidence of desmosomal gene mutations that is lower than expected, exercise itself has a disproportionate role in the pathogenesis of ‘exercise-induced ACM’. Malignant right VS associated with right dominant ACM (originally termed ‘arrhythmogenic right ventricular dysplasia’) can sometimes be suspected by the following 12-lead electrocardiogram (ECG) findings: (i) negative T-waves in V1–V4 leads and (ii) epsilon waves described as low-amplitude electrical potentials that occur at the end of or immediately after the QRS complex in the right precordial leads.16 However, diagnosis of left ventricular NVS, which is more malignant than the right ventricular one, is often difficult.12,17 Although some studies have reported inferolateral T-wave inversion and low QRS voltage in limb leads,12 standard 12-lead ECG is sometimes normal. Echocardiography often shows normal left ventricular motion, as the scar tissue usually spares endocardial tissue and is localized in the epicardial/midcardial layer of the left ventricle.17 Consequently, the diagnosis depends usually on cardiac magnetic resonance (CMR),18 specifically by observing late gadolinium enhancement (LGE) on post-contrast sequences. The presence and extent of LGE, especially subepicardial/midcardial stria pattern, are strong, independent marker of the presence of scaring and arrhythmic events in non-ischaemic heart diseases.18 However, CMR testing is notoriously expensive and requires access to cyclotron or generator for positron emission tomography (PET) tracers and thus cannot be available in all suspected patients. Therefore, we should sort out our patients before sending them to the CMR laboratories. Table 1 shows clinical parameters indicating the presence of left VS. Previous studies have put emphasis on the presence of polymorphic and right bundle branch block (RBBB) morphology VAs (indicating left ventricular origin), which can predict malignant left VAs and SCA/D.9 Also, family history of SCD and cardiomyopathy seems important, as VS is closely related with hereditary ACM.19 However, reported sensitivity of these parameters is generally not high enough to be used for the screening of VS.20 Previously reported clinical parameters indicating the presence of left ventricular scar ECG, electrocardiogram; LBBB, left bundle branch block; RBBB, right bundle branch block; SCD, sudden cardiac death; VA, ventricular arrhythmia; VT, ventricular tachycardia. Previously reported clinical parameters indicating the presence of left ventricular scar ECG, electrocardiogram; LBBB, left bundle branch block; RBBB, right bundle branch block; SCD, sudden cardiac death; VA, ventricular arrhythmia; VT, ventricular tachycardia. In the excellent article in this issue of the European Journal of Preventive Cardiology, Sciarra and coauthors20 demonstrate that 7 standard 12-lead electrocardiographic findings may indicate the presence of non-ischaemic left VS in adult athletes with non-sustained VAs of RBBB morphology. The article shows that the ECG scoring system based on their findings has high sensitivity and would not miss the patients who should be prompted CMR study for definitive diagnosis. In spite of several limitations listed in their article, their messages are precious and important in our daily practices and await further investigations.