ECG parameters predict left ventricular conduction delay in patients with left ventricular dysfunction

Early effects of left bundle branch area pacing on ventricular activation by speckle tracking echocardiography

BACKGROUND

Left bundle branch area pacing (LBBAP) is an emerging cardiac pacing modality that preserves fast electrical activation of the ventricles and provides very good electrical measures. Little is known on mechanical ventricular activation during this pacing modality.

METHODS

We prospectively enrolled patients receiving LBBAP. Electrocardiographic and electrical parameters were evaluated at implantation, < 24 h and 3 months. Transthoracic echocardiography with strain analysis was performed at baseline and after 3 months, when ventricular mechanical activation and synchrony were analyzed by time-to-peak standard deviation (TPSD) of strain curves for both ventricles. Intraventricular left ventricular (LV) dyssynchrony was investigated by LV TPSD and interventricular dyssynchrony by left ventricle-right ventricle TPSD (LV-RV TPSD).

RESULTS

We screened 58 patients with permanent pacing indication who attempted LBBAP. Procedural success was obtained in 56 patients (97%). Strain data were available in 50 patients. QRS duration was 124.1 ± 30.7 ms at baseline, while paced QRS duration was 107.7 ± 13.6 ms (p < 0.001). At 3 months after LBBAP, left ventricular ejection fraction (LVEF) increased from 52.9 ± 10.6% at baseline to 56.9 ± 8.4% (p = 0.004) and both intraventricular LV dyssynchrony and interventricular dyssynchrony significantly improved (LV TPSD reduction from 38.2 (13.6-53.9) to 15.1 (8.3-31.5), p < 0.001; LV-RV TPSD from 27.9 (10.2-41.5) to 13.9 (4.3-28.7), p = 0.001). Ameliorations with LBBAP were consistent in all subgroups, irrespective of baseline QRS duration, types of intraventricular conduction abnormalities, and LVEF.

CONCLUSIONS

Echocardiographic strain analysis shows that LBBAP determines a fast and synchronous biventricular contraction with a stereotype mechanical activation, regardless of baseline QRS duration, pattern, and LV function.

Predictors of long-term survival in Japanese patients with heart failure with reduced ejection fraction (HFrEF) treated with cardiac resynchronization therapy-defibrillators (CRT-D)

BACKGROUND

Reports on the factors predicting long-term survival of CRT-D cases from Western countries are increasing, however, those from Asia including Japan are still sparse. We aimed to clarify the factors predicting long-term survival of Japanese CRT-D cases.

METHODS

We retrospectively analyzed consecutive 133 patients who underwent CRT-D implantation between 2006 and 2021. We compared clinical factors between patients who died within 5 years after implantation (short-survival group: n = 31) and who had survived for more than 5 years (long-survival group: n = 36) after implantation.

RESULTS

Major underlying heart diseases were dilated cardiomyopathy (45%) and ischemic heart disease (12%). There was no difference between the short-survival group and the long-survival group in incidence of CLBBB (32% vs. 30%), whereas CRBBB was more common in the short-survival group (26% vs. 0%, p = .004). Mechanical dyssynchrony at implantation was more frequent in the long-survival group (48% vs. 78%, p = .02). The incidence of response to CRT at 1 year after implantation was higher in long-survival group (19% vs. 50%, p = .02). Multiple logistic regression analysis identified NYHA class, mechanical dyssynchrony at implantation, and response at one year as predictors of long-term survival.

CONCLUSIONS

In Japanese CRT-D cases, lower NHYA class, preexisting mechanical dyssynchrony, and 1-year response to CRT predict long-term survival.

Useful Electrocardiographic Signs to Support the Prediction of Favorable Response to Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is a cornerstone therapeutic opportunity for selected patients with heart failure. For optimal patient selection, no other method has been proven to be more effective than the 12-lead ECG, and hence ECG characteristics are extensively researched. The evaluation of particular ECG signs before the implantation may improve selection and, consequently, clinical outcomes. The definition of a true left bundle branch block (LBBB) seems to be the best starting point with which to select patients for CRT. Although there are no universally accepted definitions of LBBB, using the classical LBBB criteria, some ECG parameters are associated with CRT response. In patients with non-true LBBB or non-LBBB, further ECG predictors of response and non-response could be analyzed, such as QRS fractionation, signs of residual left bundle branch conduction, S-waves in V6, intrinsicoid deflection, or non-invasive estimates of Q-LV which are described in newer publications. The most important and recent study results of the topic are summarized and discussed in this current review.

Bilateral Bundle Branch Block

Left bundle branch block (LBBB) and right bundle branch block (RBBB) are classic manifestations of bundle branch conduction disorders. However, a third form that is uncommon and underrecognized may exist that has features and pathophysiology of both: bilateral bundle branch block (BBBB). This unusual form of bundle branch block exhibits an RBBB pattern in lead V1 (terminal R wave) and an LBBB pattern in leads I and aVL (absence of S wave). This unique conduction disorder may confer an increased risk of adverse cardiovascular events. BBBB patients may be a subset of patients that respond well to cardiac resynchronization therapy.

ECG optimisation for CRT systems in the era of automatic algorithms: a comprehensive review

Cardiac resynchronisation therapy (CRT) may fail in up to one third of patients, mainly due to anatomical and procedural issues. In the daily practice, ECG optimisation is largely used to address CRT delivery. Ineffective CRT can be related to non-optimal pacing timing as well as inadequate pacing-capture. A rate-competitive atrial fibrillation (AF) or a high daily burden of premature ventricular contractions (PVC) may also affect CRT by means of fusion or pseudo-fusion captures. Growing observations suggest that in a subset of patients with typical left bundle branch block (LBBB), selected LV pacing may be more effective, producing a complete fusion between the left pacing and the intrinsic right bundle activation. The His-ventricular (HV) interval is an invasive measurement (derived from electrophysiological study), which mainly reflects the RV activation (and its contribution to QRS timing) and has been proposed by some authors when addressing LV-paced–RV-sensed fusion. In sinus rhythm CRT patients, with baseline typical LBBB criteria and preserved AV conduction, the “dromotropic” management to achieve RV intrinsic activation with LV fusion is also “AV delay dependent”. In this regard, the RV intrinsic activation (detected by RV sensing) and the A (paced/sensed)-RV (sensed) interval are also influenced by the RV lead position within the RV. The current families of CRT devices have implemented automatic algorithms to optimise AV and VV timing intervals. The proof of principle is again the evidence that fusion of an LV-paced beat with intrinsic rhythm may be more beneficial than standard biventricular pacing, provided a preserved AV conduction. In the present review, all the above issues are discussed.

Bilateral Bundle Branch Block

Left bundle branch block (LBBB) and right bundle branch block (RBBB) are classic manifestations of bundle branch conduction disorders. However, a third form that is uncommon and underrecognized may exist that has features and pathophysiology of both: bilateral bundle branch block (BBBB). This unusual form of bundle branch block exhibits an RBBB pattern in lead V1 (terminal R wave) and an LBBB pattern in leads I and aVL (absence of S wave). This unique conduction disorder may confer an increased risk of adverse cardiovascular events. BBBB patients may be a subset of patients that respond well to cardiac resynchronization therapy.

Left ventricle pacing challenges in cardiac resynchronization therapy systems

Left ventricle (LV) pacing can be considered peculiar due to its different lead/tissue interface (epicardial pacing) and the small vein wedging lead locations with less reliable lead stability. The current technologies available for LV capture automatic confirmation adopt the evoked response (ER), as well as "LV pace to right ventricular (RV) sense" algorithms. The occurrence of anodal RV capture is today completely solved by the use of bipolar LV leads, while intriguing data are recently published regarding the unintentional LV anodal capture beside the cathodal one, which may enlarge the front wave of cardiac resynchronization therapy (CRT) delivery. The LV threshold behavior over time leading to ineffective CRT issues (subthreshold stimulation or concealed loss of capture), the extracardiac capture with phrenic nerve stimulation (PNS), the flexible electronic cathode reprogramming and the inadequate CRT delivery related to inadequate AV and VV pace timing (and its management by LV "dromotropic pace-conditioning") are discussed. Moreover, recently, His bundle pacing (HBP) and left bundle branch pacing (LBBP) have shown growing interest to prevent pacing-induced cardiomyopathy as well as for direct intentional CRT. The purpose of the present review is to explore these new challenges regarding LV pacing starting from old concepts.

The QR-max index, a novel electrocardiographic index for the determination of left ventricular conduction delay and selection of cardiac resynchronization in patients with non-left bundle branch block

Non-left bundle branch block (non-LBBB) remains an uncertain indication for cardiac resynchronization therapy (CRT). Non-LBBB includes right bundle branch block (RBBB) and non-specific LV conduction delay (NSCD), two different electrocardiogram (ECG) patterns which are not generally considered to be associated with LV conduction delay as judged by the invasive assessment of the Q-LV interval. We evaluated whether a novel ECG interval (QR-max index) correlated with the degree of LV conduction delay regardless of the type of non-LBBB ECG pattern, and could, therefore, predict CRT response. In 173 non-LBBB patients on CRT (92 NSCD, 81 RBBB), the QR-max index was measured as the maximum interval from QRS onset to R-wave offset in the limb leads. The correlation between QR-max index and Q-LV interval and the impact of the QR-max index on time to first heart failure hospitalization during 3-year follow-up were assessed. Q-LV correlated better with the QR-max index than with QRSd, particularly in the RBBB group (r = 0.91; p < 0.001 vs. r = 0.19; p < 0.089), while the correlations were r = 0.79 (p < 0.01) and r = 0.68 (p < 0.01), respectively, in the NSCD group. In both groups, the QR-max index was significantly more able than QRSd to identify CRT responders (AUC 0.825 vs. 0.576; p = 0.0008 in RBBB; AUC 0.738 vs. 0.701; p = 0.459 in NSCD). A QR-max index exceeding a cutoff value of 120 ms was associated with CRT response, with predictive values of 86.8 and 81.4% in RBBB and NSCD, respectively. The QR-max index reflects the degree of LV electrical delay regardless of QRS duration in RBBB and NSCD patients and is a useful indicator of suitability for CRT in non-LBBB patients.

Correlação entre a deflexão intrinsecoide, classificação clínica e parâmetros ecocardiográficos em cães com degeneração mixomatosa valvar mitral

RESUMO A degeneração mixomatosa valvar mitral (DMVM) costuma ser diagnosticada pelo ecocardiograma, porém o eletrocardiograma (ECG) pode sugerir alterações específicas e auxiliar no diagnóstico e no tratamento. A deflexão intrinsecóide (DI) é uma medida simples do ECG, que representa o início da despolarização ventricular e pode indicar a presença de sobrecargas e hipertrofia no ventrículo esquerdo. O objetivo deste trabalho é comparar dados prévios sobre condição clínica e ecocardiograma de cães com endocardiose de mitral e o valor da deflexão intrinsecóide do ECG, para buscar uma relação de concordância. Foram selecionados os arquivos de 45 cães anteriormente atendidos na rotina clínica do HV-UPFR. A estatística mostrou diferença relevante nos grupos B1, B2 e C nas derivações D2, D3, aVF, rV, V2 e V4 (P<0,05), o que permitiu classificá-los de acordo com o tamanho da DI, e esse resultado correspondeu à classificação do consenso de endocardiose de mitral em cães nesses estágios. Concluiu-se que há um aumento gradativo no valor da DI à medida que a DMVM avança, principalmente nos estágios B1, B2 e C, associado à sobrecarga e à hipertrofia ventricular esquerda, portanto esse parâmetro pode ser usado na classificação da doença.

An S wave in ECG lead V6 predicts poor response to cardiac resynchronization therapy and long-term outcome

BACKGROUND

Cardiac resynchronization therapy (CRT) is a standard treatment for selected patients with chronic heart failure (HF). However, up to 30%-50% of patients still do not respond to CRT.

OBJECTIVE

Our aim was to identify the predictive value of an S wave in lead V₆ in CRT response in patients with complete left bundle branch block (CLBBB).

METHODS

The CLBBB definition included the Strauss left bundle branch block criteria and the absence of q waves in leads I, V₅, and V₆. According to the electrocardiogram at baseline, CLBBB patients were divided into 3 groups: T-CLBBB group (CLBBB without an S wave in lead V₅ or V₆), V₅S group (CLBBB with an S wave in lead V₅ and no S wave in lead V₆), and V₅&V₆S group (CLBBB with S waves in leads V₅ and V₆). CRT response was defined as left ventricular end-systolic volume reduction ≥ 15% at 6-month follow-up. The combined end point included HF rehospitalization or all-cause death.

RESULTS

Of 181 patients with left bundle branch block-like pattern, 112 patients with CLBBB were included into 3 groups: 54 in the T-CLBBB group, 32 in the V₅S group, and 26 in the V₅&V₆S group. The CRT response rate was 85.2% (46), 65.6% (21), and 38.5% (10), respectively (P < .001). Kaplan-Meier curves demonstrated that patients in the V₅&V₆S group had a higher incidence of HF rehospitalization or all-cause death than those in the other 2 groups (P < .001). In a multivariate logistic regression model analysis, an S wave in lead V₆ was significantly associated with CRT nonresponse (hazard ratio 0.33; 95% confidence interval 0.11-0.96; P = .042).

CONCLUSION

An S wave in lead V₆ can predict poor response to CRT and long-term outcome.

Updated Clinical Evidence for Effective Cardiac Resynchronization Therapy in Congestive Heart Failure and Timing of Implant

Investigative works of the past 20 years have compiled extensive data on the effectiveness and implications of cardiac resynchronization therapy (CRT) in patients with heart failure. Since then, CRT has become a well-accepted and widely adapted adjunctive therapy for patients with heart failure with ventricular dyssynchrony. This overview discusses the updated knowledge on the benefits afforded with CRT and reviews the major clinical trials that have established CRT at its current practice. Based on the data, the indications of CRT and the timing of appropriate implant of CRT devices with respect to heart failure status will be presented.