It all starts with the ECG: cardiac MRI in combination with electrophysiological study to stratify arrhythmic risk in a patient with non-ischemic cardiomyopathy and preserved LVEF

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Stefan Ailoaei1,2,3, Carina-Gabriela Ureche1,2,3, Alex Bostan1,2, Laura Tapoi1, Dan Ursu1, Anatolie Cazacu4, Radu Sascau1,3, Cristian Statescu1,2,3, Mihaela Grecu1,2


1 Department of Cardiology, „Prof. Dr. George I. M. Georgescu” Institute of Cardiovascular Diseases, Iasi, Romania
2 Department of Electrophysiology, „Prof. Dr. George I. M. Georgescu” Institute of Cardiovascular Diseases, EHRA Recognized Training Center, Iasi, Romania
3 „Grigore T. Popa” University of Medicine and Pharmacy, Iasi, Romania
4 German Center of Diagnosis, Chisinau, Republic of Moldova


Abstract: A 45-year-old male, hypertensive and obese presented with a 3-months history of short episodes of inter-mittent palpitations. Clinical examination was unremarkable; however, the electrocardiogram documented major right bundle branch block and the presence of fragmented QRS in all precordial leads. His echocardiography documented a dilated left ventricle, with mild systolic dysfunction and moderate biventricular reduction of the global longitudinal strain. On angiography, the epicardial coronary arteries were normal. A cardiac MRI revealed diffuse transmural fibrotic lesions with non-ischemic pattern of the ventricles, suggestive of chronic myocarditis. The electrophysiological study induced two ventricular tachycardia morphologies which were ablated and an ICD for sudden cardiac death primary prevention was implanted. Fortunately, at 6 months follow-up our patient had no ICD therapies and reported an alleviation of symptoms. Keywords: myocarditis, risk stratification, electrophysiology study, ICD, primary prevention.

Rezumat:    Pacient în vârsta de 45 ani, obez, hipertensiv se prezintă pentru un istoric de 3 luni de episoade de palpitaţii cu ritm rapid, rare şi izolate, fără crize susţinute. Examenul clinic nu relevă particularităţi, însă electrocardiograma de repaus documentează prezenţa unui bloc major de ramură dreaptă şi complexe QRS fragmentate în toate derivaţiile precordiale. Ecocardiografic, ventriculul stâng este dilatat, cu funcţie sistolică globală uşor diminuată şi strain global longitudinal biventricular redus. Angiografia coronariană relevă artere coronare epicardice normale. Imagistica prin rezonanţă magnetică cardiacă (IRMC) scoate la iveală leziuni fibrotice difuze transmurale cu dispoziţie non-ischemică, sugestive pentru diagnosticul de miocardită cronică. Studiul electrofiziologic induce două morfologii de tahicardie ventriculară, care au fost ablate, iar ulterior a fost implantat un defibrilator cardiac (ICD) în prevenţia primara a mortii subite cardiace. Rezultatul post-ablaţie a fost unul favorabil, întrucât la urmărirea de la 6 luni pacientul declară îmbunătăţirea semnificativă a simptomatologiei, iar interogarea ICD nu a documentat nicio terapie. Cuvinte-cheie: miocardită, stratifi carea riscului, studiu electrofiziologic, DCI, prevenţia primară.

  1. PATIENT PRESENTATION

A 44-year-old gentleman, a sales agent, known hyper-tensive, obese and dyslipidemic presented with a 3-months history of fatigue and palpitations of abrupt onset and termination, a duration of up to 1 minute, accompanied by dyspnea. His home medication inclu-ded Candesartan 8 mg OD and Atorvastatin 10 mg OD. The physical examination was within normal li-mits, with a blood pressure of 130/80 mmHg, regular heart rate of 92 bpm, SpO2 of 100% on room air and temperature of 37ºC. The patient was a non-smoker with no history of drug abuse, previous heart surgery, recent invasive procedures or dental intervention.

Figure 1. ECG at presentation: Sinus rhythm 63/min, major right bundle branch block, QRS fragmentation in precordial leads.

Figure 2. Longitudinal Strain Bull’s eye: moderately reduced GLS (-15.5%).

  1. INITIAL WORK UP

Laboratory tests revealed elevated lipid profile (cho-lesterol 235 mg/dl, LDL cholesterol 171 mg/dl, tri-glycerides 180 mg/dl), but otherwise normal complete blood count, inflammatory markers, liver, renal and thyroid function. In spite of the normal physical exami-nation and blood tests, the electrocardiogram (ECG) showed sinus rhythm 90 bpm, QRS axis at 0 degrees and major right bundle branch block with notching in the nadir of the S wave in all precordial leads. A transthoracic echocardiogram (TTE) was performed and documented mildly dilated left ventricle (LV), with mild systolic dysfunction (ejection fraction (EF) of 45%) and moderate reduction of the global longi-tudinal strain (GLS -15%), as well as a moderate re-duction of the right ventricular (RV) GLS (-14%). On angiography, the epicardial coronary arteries presen-ted no signifi cant lesions. A Holter monitoring revea-led no malignant ventricular arrhythmias, but frequent polymorphic ventricular premature beats (VPB) (4000 VPBs/24 hour).

  1. DIAGNOSIS AND MANAGEMENT

In view of a high suspicion of a non-ischemic cardi-omyopathy, the patient underwent a cardiac MRI1. Surprisingly, it revealed biventricular diffuse transmu-ral fibrotic lesions with non-ischemic pattern, sugges-tive for post-myocarditis sequelae. In addition, it con-firmed the moderate reduction in both the right and left ventricular global longitudinal strain shown on the echocardiography. Lesions transmurality together with reduced strain values and high number of viable myocardial channels within the scar (potential reentry circuits), suggested our patient was at high risk for sudden cardiac death (SCD) due to malignant ventri-cular arrhythmias, despite its preserved LVEF. In this regard, an electrophysiological (EP) study was per-formed, which induced two ventricular tachycardia

morphologies, with hemodynamic compromise, re-quiring urgent electrical cardioversion. An endocardial radiofrequency ablation was performed, guided by ar-rhythmogenic substrate mapping, targeting abnormal potentials within the scar and at its borders. At the end of the procedure the induction protocol was ne-gative for monomorphic ventricular tachycardia, but ventricular fibrillation was still inducible, so an ICD was implanted shortly after for the SCD primary pre-vention.

Figure 3. Late gadolinium enhancement short axis view: diffuse fibrosis on the LGE images

Figure 4. The two VT morphologies. Deterioration to VF.

  1. FOLLOW-UP

The patient was discharged under a small dose of Ami-odarone (100 mg OD) for 3 months post-ablation, gi-ven the inducibility of ventricular fibrillation at the end of the electrophysiological study and high myocardial excitability, and received the standard treatment for chronic heart failure (Carvedilol 6.25 mg BID, Eplere-none 50 mg OD, Candesartan 8 mg OD) and dyslipide-mia (Atorvastatin 10 mg OD), reporting an alleviation of the palpitations. The 6 and 12 months ICD follow-up showed no sustained ventricular arrhythmias. A repeat ECG and Holter was performed documenting ventricular extrasystole with origins from both RV and LV, but with a reduction in the number of VPBs (1500 VPBs/24 hours). Despite the apparent improvement of the symptoms, a repeat TTE was performed showing a further decrease in the GLS of the LV (-10%), sugges-ting the progression of the disease and the patient was further referred for extensive investigations (genetic, immunologic). A repeat CMR would have been help-ful in this case, to reveal whether there is persistent disease activity despite normal cardiac enzymes and inflammatory markers. In this regard, it is especially helpful in identifying high-risk patients and has pro-gnostic value. Unfortunately, our patient has not had further CMR evaluation until this point in time.

Figure 5. 3D fibrosis, ADAS software images imported into CARTO; red colour = scar; blue color = normal myocardium.

  1. CONCLUSIONS

This case underlines the importance of recognizing the presence of fragmented QRS on the 12-lead ECG in apparently healthy subjects, as an indicator of myocardial scarring and a high risk of adverse cardiac events2. Furthermore, speckle-tracking imaging in cardiomyo-pathies may serve as a non-invasive tool during follow up, potentially revealing substrate progression. SCD risk stratification in non-schemic cardiomyopathi-es patients with preserved ejection fraction remains a challenge. In this regard, the presence of negative prognostic factors on cardiac MRI such as a reduction in the strain values, the presence of arrhythmogenic substrate (scar size, transmurality, intra-scar viable myocardial channels), in combination with a positive EP study (induction of sustained monomorphic ven-tricular tachycardia or ventricular fibrillation) could identify SCD high risk patients that could benefit from ICD in primary prevention, despite preserved LVEF1,3.

Conflict of interest: none declared.

Figure 6. Follow up ECG. VPBs originating from both ventricles.

Figure 7. Follow up strain showing progression of the disease.

References
1. Gatzoulis Konstantinos A. et al. Primary Prevention of Sudden Car-diac Death in a Nonischemic Dilated Cardiomyopathy Population. Circ. Arrhythm. Electrophysiol. 6, 504–512 (2013).
2. Akhtar, M. & Elliott, P. M. Risk Stratification for Sudden Cardiac Death in Non-Ischaemic Dilated Cardiomyopathy. Curr. Cardiol. Rep. 21, 155 (2019).
3. Ghannam, M. et al. Risk stratification in patients with nonischemic cardiomyopathy and ventricular arrhythmias based on quantification of intramural delayed enhancement on cardiac magnetic resonance imaging. J. Cardiovasc. Electrophysiol. 31, 1762–1769 (2020).

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