Comparing the findings and diagnostic sensitivity of cardiovascular magnetic resonance in biopsy confirmed acute myocarditis with infarct-like vs. heart failure presentation.

BACKGROUND: Cardiovascular magnetic resonance (CMR) is considered the reference imaging modality in providing a non-invasive diagnosis of acute myocarditis (AM), as it allows for the detection of myocardial injury associated with AM. However, the diagnostic sensitivity and pattern of CMR findings appear to differ according to clinical presentation. METHODS: This is a retrospective cross-sectional study. Consecutive adult patients presenting to a single tertiary centre in South Africa between August 2017 and January 2022 with AM confirmed on endomyocardial biopsy (EMB) were enrolled. Patients with infarct-like symptoms, defined as those presenting primarily with chest pain syndrome with associated ST-T wave changes on electrocardiogram, or heart failure (HF) symptoms, defined as clinical signs and symptoms of HF without significant chest discomfort, were compared using contrasted CMR and parametric techniques with EMB confirmation of AM as diagnostic gold standard. RESULTS: Forty-one patients were identified including 23 (56%) with infarct-like symptoms and 18 (44%) with HF symptoms. On CMR, the infarct-like group had significantly higher ejection fractions of both ventricles (LVEF 55.3 ± 15.3% vs. 34.4 ± 13.5%, p < 0.001; RVEF 57.3 ± 10.9% vs. 42.9 ± 18.2%, p = 0.008), without significant differences in end diastolic volumes (LVEDVI 82.7 ± 30.3 ml/m2 vs. 103.4 ± 35.9 ml/m2, p = 0.06; RVEDVI 73.7 ± 22.1 ml/m2 vs. 83.9 ± 29.9 ml/m2, p = 0.25). Myocardial oedema was detected more frequently on T2-weighted imaging (91.3% vs. 61.1%, p = 0.03) and in more myocardial segments [3.0 (IQR 2.0-4.0) vs. 1.0 (IQR 0-1.0), p = 0.003] in the infarct-like group. Despite the absence of a significant statistical difference in the prevalence of late gadolinium enhancement (LGE) between the two groups (95.7% vs. 72.2%, p = 0.07), the infarct-like group had LGE detectable in significantly more ventricular segments [4.5 (IQR 2.3-6.0) vs. 2.0 (IQR 0-3.3), p = 0.02] and in a different distribution. The sensitivity of the original Lake Louise Criteria (LLC) was 91.3% in infarct-like patients and 55.6% in HF patients. When the updated LLC, which included the use of parametric myocardial mapping techniques, were applied, the sensitivity improved to 95.7% and 72.2% respectively. CONCLUSION: The pattern of CMR findings and its diagnostic sensitivity appears to differ in AM patients presenting with infarct-like and HF symptoms. Although the sensitivity of the LLC improved with the addition of parametric mapping in the HF group, it remained lower than that of the infarct-like group, and suggests that EMB should be considered earlier in the course of patients with clinically suspected AM presenting with HF.

Routine use of fluoroscopic and real-time transthoracic echocardiographic guidance to ensure safety of right ventricular endomyocardial biopsy in a low-volume center.

To determine whether the routine use of real-time transthoracic echocardiographic (TTE) guidance in addition to fluoroscopy would ensure the safety of right ventricular endomyocardial biopsy (RV EMB) in a low-volume center. RV EMB is a valuable tool and plays an important role in the diagnosis and management of patients with myocardial diseases. However, it has yet to gain widespread acceptance due to its perceived low diagnostic yield and concerns regarding its invasive nature and potential complications. Although the safety of EMB when performed by experienced operators in high-volume centers is well established, the complication rate in low-volume centers is less well defined but appears to be higher. This is a retrospective single-center cross-sectional study. Consecutive adult patients who underwent RV EMB procedures at Tygerberg Hospital (Cape Town, South Africa) between August 2017 and December 2020 were included. RV EMB was successfully performed in 85 patients. No major complications were reported. Five (5.88%) patients experienced minor complications: three transient right bundle branch blocks and two hemodynamically stable ventricular tachycardia. A definitive biopsy diagnosis was made in 37 (43.54%) patients. The average procedural time was 27.06 min, which equated to 4.09 min per specimen taken. The routine use of real-time TTE guidance in addition to fluoroscopy ensured the safety of RV EMB in a low-volume center without unnecessarily prolonging procedural time.