Genetic Characterization of Dilated Cardiomyopathy in Romanian Adult Patients

Dilated cardiomyopathy (DCM) represents a group of disorders affecting the structure and function of the heart muscle, leading to a high risk of heart failure and sudden cardiac death (SCD). DCM frequently involves an underlying genetic etiology. Genetic testing is valuable for risk stratification, treatment decisions, and family screening. Romanian population data on the genetic etiology of DCM are lacking. We aimed to investigate the genetic causes for DCM among Romanian adult patients at tertiary referral centers across the country. Clinical and genetic investigations were performed on adult patients presenting to tertiary hospitals in Romania. The genetic investigations used next-generation sequencing panels of disease-associated DCM genes. A total of 122 patients with DCM underwent genetic testing. The mean age at DCM diagnosis was 41.6 ± 12.4 years. The genetic investigations identified pathogenic or likely pathogenic variants in 50.8% of participants, while 25.4% had variants of unknown significance. Disease-causing variants in 15 genes were identified in people with DCM, with 31 previously unreported variants. Variants in TTN, LMNA, and DSP explained 75% of genetic causes for DCM. In total, 52.4% of patients had a family history of DCM/SCD. Left ventricular ejection fraction of <35% was observed in 41.9% of patients with disease-causing variants and 55% with negative or uncertain findings. Further genotype-phenotype correlations were explored in this study population. The substantial percentage (50.8%) of disease-causing variants identified in patients with DCM acknowledges the importance of genetic investigations. This study highlights the genetic landscape in genes associated with DCM in the Romanian population.

P1168Redefining first degree AV block: constant fusion pacing CRT is easier in longer PR interval patients

Background

LV only pacing is non-inferior to BiV pacing, and recent publications showed that DDD CRT without RV lead is safe in patients with normal atrioventricular (AV) conduction, although there are no device algorithms available for fusion pacing and PR interval variability is understudied in this population. Purpose: To analyse AV behaviour in pts with DDD CRT and the impact to effective fusion maintenance.

Methods

Consecutive pts with right atrium/left ventricle (RA/LV) DDD CRT pacing system were included. Prospective data were collected at every 6 months follow-up visits: device interrogation, exercise test (ET), echocardiography. CRT assessment during ET analysed loss of LV capture with special focus on maintaining constant fusion pacing during exercise. We defined 2 groups of pts: longer PR interval pts (200-250 ms) and normal PR interval pts (˂200 ms). In case of LV loss of capture or unsatisfactory LV fusion pacing, device reprogramming was performed individualised for each patient and BB/ivabradine dose titration was done to achieve stability of PR spontaneous interval. Patients were rescheduled in no later one month to be reassessed by ET.

Results

55 pts (29 male) aged 62 ± 11 y.o. were included, 36 pts with normal PR and 19 pts with longer PR. During follow-up (45 ± 19 months), a total of 235 ETs were performed with mean exercise load 118 ± 35 watts. In the normal PR group 14 pts (39%) had inadequate pacing or loss of LV capture during ET due to physiological shortening of PR interval vs. 4 pts (21%) in the long PR group. Loss of LV capture by exceeding maximum tracking rate (MTR) was noted in 6 pts (17%) with normal PR vs. 2 pts (11%) with longer PR. Post ET device optimisation included:  reprogramming rate adaptive AV interval (23 ± 8 ms decrease in normal PR pts vs. 12 ± 7 ms in longer PR pts, p &lt; 0.0001) and individualised programming of MTR. BB/ivabradine optimisation was performed in 32% of pts with normal PR vs. 13% of pts with longer PR.

Conclusions

A lower rate of optimisations after exercise test was needed in pts with a slightly longer AV conduction to achieve stability of fusion pacing DDD CRT without device algorithms. Larger studies are needed to assess AV conduction variability and the benefits of fusion pacing CRT in pts with longer PR interval.

Abstract Figure.

416 LV only fusion pacing CRT without RV lead induces size and shape LA reverse remodelling

Background

Adaptive CRT pacing induces significant left atrium (LA) reverse remodelling comparing to biventricular (BiV) pacing, although the algorithm delivers compulsory BiV pacing in heart rate over 100/min! Purpose: to assess LA remodelling in LV only pacing without RV lead in a real-life situation of permanent CRT fusion pacing.

Methods

Prospective data were analysed from a cohort of patients with CRT-P indication implanted with right atrium/left ventricle (RA/LV) DDD pacing system. Complete follow-up at every 6 months included device interrogation, exercise test, transthoracic echocardiography (TE) and individualised drug optimisation. LA evaluation included: parasternal dimension (LAd), 4 chambers view: mid-LA transverse diameter (LAt), basal LA maximal transverse diameter (LAb); volume (LA vol) and shape assessment: trapezoidal LA shape was defined by LAt less than Lab, the reverse situation was considered ellipsoidal shape.

Results

55 pts (30 males) with idiopathic DCM aged 62 ± 11 y.o. were included. Baseline characteristic: QRS 164 ± 18 ms; EF 27 ± 5.2%; mitral regurgitation was severe in 22 pts, moderate in 27 pts and mild in 6 pts; 15 pts had type III diastolic dysfunction, 37 pts with type II diastolic dysfunction, 3 pts with type I diastolic dysfunction. Average follow-up was 42 ± 18 months: all patients were responders, EF increased at 37 ± 7.9%; mitral regurgitation decreased in 38 pts (69%), diastolic profile improved in 36 pts (65%). Trapezoidal LA shape was documented in 31 (56%) patients. Atrial fibrillation was noted in 4 pts (7%) and cardioversion was needed. Non-sudden cardiac death occurred in 5 patients (9%), all deaths were noted in pts with severe LA vol, trapezoidal shape and type III diastolic dysfunction. Statistically significative LA reverse remodelling was noted regarding LA volume, but not shape.

Conclusions

RA/LV fusion CRT pacing was associated with important LA reverse remodelling and a low incidence of AF. Larger randomised studies are needed to validate these results and assess the role of LA shape remodelling in CRT.

before RA/LV CRT-P Follow-up 42 ± 18 months p LV EF, %, mean ± SD 27 ± 5.2 37 ± 7.9 &lt;0.0001 LA diameter (mm), mean ± SD 50 ± 4.9 44 ± 2.8 &lt;0.0001 LA area (cm2), mean ± SD 24 ± 5.6 22 ± 0.7 0.0138 LA volume (ml), mean ± SD 104.9 ± 34 80 ± 28.2 0.0001

Abstract 416 Figure.

Exercise test is essential in LV-only fusion CRT pacing without right ventricle lead

Purpose: Left ventricle (LV)-only pacing is non-inferior to biventricular pacing but permanent fusion pacing is needed to ensure cardiac resynchronization therapy (CRT) responsiveness. The role of systematic exercise testing (ET) in these patients has not been established. This study was designed to assess clinical and therapeutic implications (device programming/drugs) of systematic ET in patients requiring fusion-pacing CRT without an right ventricle (RV) lead. Methods: Consecutive patients with a right atrium/LV-only dual-chamber (DDD) pacing system were included. Prospective data were obtained: device interrogation, ET, and echocardiography at every 6-month follow-up visit. CRT assessment during ET included maximal heart rate, beat-to-beat echocardiography analysis of LV fusion pacing, LV loss of capture, and improvement in exercise capacity. If LV loss of capture or unsatisfactory LV fusion pacing occurred, reprogramming was individualized for each patient and ET redone. Results: A total of 55 patients (29 male) aged 62±11 years were included. During follow-up (39±18 months), a total of 235 ETs were performed, with mean exercise load 6.4±1.3 metabolic equivalents of task (118±35 W, maximal heart rate 119±17 beats/min). Twenty patients (36%) had inadequate pacing or loss of LV capture during ET, due to exceeding the maximum tracking rate (11%), chronotropic incompetence (7%), and LV pacing outside the fusion-pacing band (18%), caused by physiological shortening of the PR interval or exagerated LV preexcitation during maximum exercise. Post-ET CRT-device optimization included reprogramming of rate-adaptive atrioventricular interval (total decrease 23±8 ms), individualized programming of maximum tracking rate, or rate-response function. Drug optimization was performed in 32% of patients, and ET redone in 36%. Conclusion: In one of three ETs, an intervention in device and medication optimization was done to ensure a better outcome. Routine ET should be a standard approach to maximize fusion-pacing CRT response during follow-up.