Clinical Significance of Postoperative Atrial Fibrillation in Hypertrophic Cardiomyopathy Patients Undergoing Septal Myectomy

BACKGROUND

The optimal management of hypertrophic cardiomyopathy (HCM) patients with postoperative atrial fibrillation (POAF) after surgical myectomy remains unknown. We sought to investigate the association between POAF and atrial fibrillation (AF) or cardioembolic events during follow-up to bridge this gap.

METHODS

Patients undergoing surgical myectomy at 2 HCM referral centres in North America from 2002 to 2020 were included in this study. Patients with preoperative AF were excluded. POAF was defined as any episode of AF within 30 days after surgery.

RESULTS

Of 1176 patients, 375 (31.9%) had POAF. Age (adjusted hazard ratio [HR] 1.05, 95% confidence interval [CI] 1.03-1.06; P < 0.001), premyectomy left atrial diameter (LAD; adjusted HR 1.6, 95% CI 1.32-2.02; P < 0.001), and smoking (adjusted HR 1.60, 95% CI 1.17-2.20; P = 0.001) were associated with POAF on multivariable analysis. Of 934 patients with follow-up data, of duration 4.3 ± 4.1 years, AF was detected in 86 (9.2%). Only POAF (HR 4.20, 95% CI 2.44-7.23; P < 0.001), previous history of stroke (HR 4.81, 95% CI 1.63-14.17; P = 0.01), and postmyectomy LAD (HR 1.80, 95% CI 1.21-2.70; P = 0.004) were associated with AF incidence during follow-up. Cardioembolic events occurred in only 15 patients (1.6%). POAF was not associated with increased cardioembolic risk, with only 3 patients with POAF suffering such an event, all more than 4 years after surgery.

CONCLUSIONS

POAF is common in HCM patients undergoing myectomy and is a predictor of AF during follow-up. Over long-term follow-up, cardioembolic events are uncommon. These findings suggest that routine long-term anticoagulation for all HCM patients with postmyectomy AF is not justified after the initial postoperative period.

Association of duration and intensity of exercise with phenotypic expression in hypertrophic cardiomyopathy

OBJECTIVES

There is limited data regarding the impact of exercise on phenotypic expression in hypertrophic cardiomyopathy (HCM). We aimed to investigate whether such an association exists in a cohort of genotype-positive HCM patients.

METHODS

In this cross-sectional study of genotype-positive HCM families, we used structured questionnaires to obtain data regarding intensity and duration of exercise of participants starting at the age of 10, as well as data regarding exercise recommendations and their impact on quality of life (QOL). The association of cumulative metabolic-equivalent hours of exercise at different ages with different measures of phenotypic expression (maximal wall thickness, left atrial diameter, extent of late gadolinium enhancement) was analyzed.

RESULTS

The study included 109 patients from 55 families, including 43 male (39%) and 90 (83%) phenotype-positive. No association was identified between exercise duration or intensity with any of the phenotypic markers with the exception of greater cumulative exercise associated with younger age at presentation. Similar results were obtained when analysis was limited to exercise until the age of 20, until the age of 30 or only after 30. Among phenotype-positive patients, 89% recalled receiving recommendations regarding exercise restriction, 29% noted reduction in exercise level following such recommendations and 25% noted this having a significant impact on their QOL.

CONCLUSION

We found no association between exercise intensity or duration and phenotypic expression in genotype-positive HCM patients. These findings are important for physician-patient discussions and support the recent trend towards more permissive exercise restrictions in HCM.

Clonal hematopoiesis confers an increased mortality risk in orthotopic heart transplant recipients

Novel risk stratification and non-invasive surveillance methods are needed in orthotopic heart transplant (OHT) to reduce morbidity and mortality post-transplant. Clonal hematopoiesis (CH) refers to the acquisition of specific gene mutations in hematopoietic stem cells linked to enhanced inflammation and worse cardiovascular outcomes. The purpose of this study was to investigate the association between CH and OHT. Blood samples were collected from 127 OHT recipients. Error-corrected sequencing was used to detect CH-associated mutations. We evaluated the association between CH and acute cellular rejection, CMV infection, cardiac allograft vasculopathy (CAV), malignancies, and survival. CH mutations were detected in 26 (20.5%) patients, mostly in DNMT3A, ASXL1, and TET2. Patients with CH showed a higher frequency of CAV grade 2 or 3 (0% vs. 18%, p < .001). Moreover, a higher mortality rate was observed in patients with CH (11 [42%] vs. 15 [15%], p = .008) with an adjusted hazard ratio of 2.9 (95% CI, 1.4-6.3; p = .003). CH was not associated with acute cellular rejection, CMV infection or malignancies. The prevalence of CH in OHT recipients is higher than previously reported for the general population of the same age group, with an associated higher prevalence of CAV and mortality.

Left atrial remodelling after septal myectomy is associated with a reduced 5-year risk of atrial fibrillation in hypertrophic cardiomyopathy

Background

Left atrial diameter (LAD) is an established predictor of atrial fibrillation (AF) and adverse outcomes in hypertrophic cardiomyopathy (HCM). However, the impact of LAD remodelling after surgical myectomy on the development of late onset AF is still poorly understood.

Purpose

To investigate the association between LAD remodelling and new occurrence of AF in the first five years after surgical myectomy in a large patient population with HCM.

Methods

1177 HCM patients without a history of AF, subjected to surgical myectomy at two referral centres between 2001 and 2020 were retrospectively reviewed. Paired echocardiographic studies before and shortly after surgical myectomy were available in 894 (76%) patients and 889 (75%) patients had complete LAD measurements, defined as the anteroposterior diameter at end-systole from parasternal long axis view. LAD was considered normal when ≤40mm. Late onset AF was determined as AF documented between one month and 5 years follow up after myectomy. Patients were grouped as having normal LAD pre- and post-myectomy (group 1), enlarged pre-myectomy LAD but normal post-myectomy LAD (group 2), and those with enlarged LAD post-myectomy (group 3). Cox proportional hazards models were applied to evaluate the impact of LAD on late onset AF.

Results

Late onset AF was detected in 63 (7%) patients, 56% male, with an incidence of 1%/year. Patients with AF were older (56±13 vs. 52±14 years, p=0.03), had a larger post-surgery LAD (44±7 vs. 41±6 mm, p&lt;0.001) and a lower left ventricular ejection fraction (58±6 vs. 61±6%, p=0.002) compared to patients without AF. Postoperative left ventricular maximal wall thickness (14±4 mm vs. 15±4mm, p=0.53), left ventricular outflow tract obstruction (6% vs. 8%, p=0.49) or moderate/severe mitral regurgitation (13% vs. 9%, p=0.29) were similar between patients with and without late onset AF. Among the 227 patients in group 1, late onset AF occurred in only 5 (3%), in comparison to 8 (5%) of 182 patients in group 2, and in 36 (10%) of the 480 patients in group 3 (p=0.006). Using group 1 as reference, the hazard ratio for developing AF was 2.1 (95% CI 0.7–6.5, p=0.15) for patients in group 2 and 3.5 (95% CI 1.4–9.4, p=0.005) for patients in group 3.

Conclusion

In our study we were able to show that the overall post-myectomy 5-year risk for developing AF was 1%/year. Normal LAD and reverse LAD remodelling correlated with a lower risk for developing late onset AF, whereas a higher risk was associated with enlarged post-myectomy LAD. These results highlight the possible clinical benefit of LAD remodelling after myectomy in reducing late onset AF.

Funding Acknowledgement

Type of funding sources: None.

Non-invasive assessment of right ventricular function and pulmonary pressures in cardiogenic shock remains challenging: don't pack away the PAC just yet

Background

Cardiogenic shock (CS) is associated with high levels of morbidity and mortality despite advances in treatment. Patients with right ventricle (RV) dysfunction have been shown to have poorer outcomes. It is suggested that invasive monitoring through pulmonary artery catheter (PAC) placement can assist in guiding management to improve survival, though they are associated with adverse events.

Purpose

This study assessed the utility of non-invasive, echocardiographic assessment of RV performance and pulmonary artery pressures (PAP) in patients with CS.

Methods

Consecutive patients admitted to a North American quaternary cardiac intensive care unit who had PAC placement were recruited into this study. Invasive haemodynamic assessment was followed by transthoracic echocardiography (TTE) performed by a critical care cardiologist, blinded to the invasive measurements. TTE images were later reported by a second cardiologist, blinded to the invasive measurements and the patient. Correlations between RV and pulmonary invasive and non-invasive parameters were evaluated using Pearson's correlation.

Results

Overall, 96 assessments of 60 patients were compared. Patients were predominantly male (73%), aged 58±14 years and SCAI stage C (55%) and D (22%) at the time of assessment. Invasive measurements of right heart and pulmonary function was possible in all patients. Mean RAP was 8.5±4.7 mmHg, systolic PAP 37.5±9.9 mmHg, diastolic PAP 18.1±6.5 mmHg, mean PAP 25.1±7.2 mmHg, pulmonary capillary wedge pressure (PCWP) 16.0±16.4 mmHg, pulmonary vascular resistance (PVR) 157±99dyn s cm–5, RV stroke work index (RVSWI) 7.0±3.9 g min/m2 and PAP index (PAPi) 2.9±4.2. When compared to non-invasive echocardiographic parameters, there was little correlation with invasive values (Table). RVSWI moderately correlated with peak tricuspid regurgitation (TR) velocity, tricuspid annular plane systolic excursion (TAPSE) and estimated systolic PAP; while peak TR velocity was mild-moderately correlated with PAP and PCWP. No single non-invasive parameter demonstrated strong prediction of invasive values.

Conclusion

Non-invasive assessment of right heart and pulmonary haemodynamic parameters is of limited validity when compared with invasive monitoring through PAC in patients with CS. PAC remains the most reliable method of assessing the RV haemodynamic profile in CS. Future studies should evaluate the clinical benefit of invasive haemodynamic monitoring in this population.

Funding Acknowledgement

Type of funding sources: None.

Echocardiographic assessment alone is inadequate for determining elevated left sided filling pressures in patients with cardiogenic shock

Background

Left atrial (LA) filling pressure assessment is of paramount importance in tailoring treatments for patients with cardiogenic shock (CS). ESC guidelines advocate for the use of mitral inflow Doppler and mitral annulus tissue Doppler measurements to predict elevated left atrial pressure in clinical practice. Echocardiographic measurement of LA pressures could reduce the need for invasive monitoring in CS patients, but its utility remains unproven in this population.

Purpose

We assessed the validity of mitral inflow velocity and mitral annulus velocity indices to determine LA pressures, correlating them with invasive measurement of pulmonary capillary wedge pressure (PCWP) in CS patients admitted to the cardiac intensive care unit (CICU).

Methods

We prospectively evaluated consecutive patients who underwent pulmonary artery catheter insertion in the CICU, measuring their haemodynamic parameters, including PCWP. This was immediately followed by a transthoracic echocardiography (TTE) performed by a critical care cardiologist, blinded to the invasive measurements. The early (E) and late (A) mitral inflow velocities were measured using mitral inflow Doppler and septal and lateral mitral annulus velocities (e') were measured using tissue Doppler, all in the apical 4-chamber view. TTE images were later reported by a second cardiologist, blinded to the invasive measurements and the patient. Correlations between E; E/A ratio; E/e' ratio and PCWP were evaluated using Pearson's correlation.

Results

Sixty patients were recruited into the study, aged 58±14 years, 27% female, with 96 assessments undertaken. The majority (55%) of patients were SCAI stage C, with 14% having had a cardiac arrest prior to CICU admission and 27% required mechanical ventilation at the time of assessment. Mean PCWP was 16.0±6.5 mmHg. Full mitral valve Doppler and tissue Doppler profiles were measured in 67 (70%) assessments, limited due to E/A fusion, atrial fibrillation and limited acoustic windows. There was only weak correlation between PCWP and E/A ratio (R=0.33, p=0.01), with no correlation between PCWP and the other measured values (Table 1), including E/e'. The AUC for identifying patients with elevated PCWP (≥15 mmHg) using E/A ratio was 0.67 (p=0.02), although there was no suitable value to use as a cut off with adequate sensitivity and specificity (Figure 1).

Conclusion

Echocardiographic non-invasive assessment of left sided cardiac filling pressures is technically challenging in patients with CS. Even when possible, there is weak correlation between echocardiographic and invasive measurements, suggesting limited value in this technique. Alternative non-invasive modalities, such as lung ultrasound, should be investigated in this population to assist clinical assessment.

Funding Acknowledgement

Type of funding sources: None.

Lung ultrasound predicts left-sided filling pressures in patients with cardiogenic shock admitted to the cardiac intensive care unit

Background

Left and right filling pressures, as well as cardiac output, are key targets in optimising treatment of cardiogenic shock (CS). Invasive pulmonary artery catheters can provide these data but are associated with complications and are not available in all hospital settings. Lung ultrasound (LUS) can detect pulmonary congestion in patients with heart failure (HF) and may be an alternative to invasive monitoring. We assessed the correlation between LUS score and invasive haemodynamic parameters in patients with CS admitted to the cardiac intensive care unit (CICU) of a North American cardiac centre.

Methods

We prospectively evaluated consecutive patients who underwent pulmonary artery catheter insertion in the CICU. Haemodynamic parameters including right atrial pressure (RAP) and pulmonary capillary wedge pressure (PCWP) were measured and cardiac output (CO) was calculated using the thermodilution method. This was immediately followed by an 8-zones LUS done by a critical care cardiologist who was blinded to the invasive hemodynamic measurements. The LUS score was calculated by counting the total number of B-lines in all 8 zones, with a higher score indicating greater congestion. Correlations between LUS score and hemodynamic parameters were evaluated using Pearson's correlation.

Results

Ninety-six measurements from 60 patients were included, aged 58±14 years with 27% female. The most common diagnosis at admission was cardiogenic shock, followed by acute myocardial infarction and HF exacerbation. Most patients were at SCAI stages C and D at the time of assessment. The mean number of B-lines at LUS was 10.1±8.2. Mean RAP was 8.5±4.6 mmHg, PCWP 16.2±6.3 mmHg and CO of 5.0±1.8 L/min. The total number of B-lines was correlated with PCWP (r=0.66, P&lt;0.001, see Figure 1), RAP (r=0.26, P&lt;0.001) and cardiac output (r=−0.23, p=0.02). Due to the correlation of B-lines in LUS with PCWP, we then evaluated the area under the ROC of the LUS to identify patients with PCWP ≥15 mmHg. The number of positive zones (≥3 B-lines) showed an AUC of 0.81 (0.72–0.89), P&lt;0.001. In 36 patients, we had repeated measurement with more than 12 hours apart. The delta change in PCWP was correlated with delta change in the number of B-lines (r=0.59, P&lt;0.001).

Conclusion

Elevated LUS score in patients with CS is associated with worse invasively-measured LV filling pressures, but less so with RAP or CO. LUS can serve as a useful adjunct to the clinical assessment of patients with CS who do not receive invasive hemodynamic monitoring, either at a single timepoint or to detect changes in clinical status over time, to guide ongoing management.

Funding Acknowledgement

Type of funding sources: None.

Patient Outcomes and Characteristics in a Contemporary Quaternary Canadian Cardiac Intensive Care Unit

Background

The modern-day cardiac intensive care unit (CICU) has evolved to care for patients with acute critical cardiac illness. We describe the current population of cardiac patients in a quaternary CICU.

Methods

Consecutive CICU patients admitted to the CICU at the Toronto General Hospital from 2014 to 2020 were studied. Patient demographics, admission diagnosis, critical care resources, complications, in-hospital mortality, and CICU and hospital length of stay were recorded.

Results

A total of 8865 consecutive admissions occurred, with a median age of 64.9 years. The most common primary cardiac diagnoses were acute decompensated heart failure (17.8%), non ST-elevation myocardial infarction (16.8%), ST-elevation myocardial infarction (15.5%), and arrhythmias (14.7%). Cardiogenic shock was seen in 13.2%, and out-of-hospital cardiac arrest in 4.1%. A noncardiovascular admission diagnosis accounted for 13.9% of the cases. Over the period studied, rates of admission were higher for cardiogenic shock (P < 0.001 for trend), with a higher use of critical care resources. Additionally, rates of admission were higher in female patients and those who had chronic kidney disease and diabetes. The in-hospital mortality rate of all CICU admissions was 13.2%, and it was highest in those with noncardiac conditions, compared to the rate in those with cardiac diagnoses (29.4% vs 10.6%, P < 0.001).

Conclusions

Given the trends of higher acuity of patients with cardiac critical illness, with higher use of critical care resources, education streams for critical care within cardiology, and alternative pathways of care for patients who have lower-acuity cardiac disease remain imperative to manage this evolving population.

Clonal haematopoiesis is associated with higher mortality in patients with cardiogenic shock

AIMS

Cardiogenic shock (CS) with variable systemic inflammation may be responsible for the patient heterogeneity and the exceedingly high mortality rate. Cardiovascular events have been associated with clonal haematopoiesis (CH) where specific gene mutations in hematopoietic stem cells lead to clonal expansion and the development of inflammation. This study aims to assess the prevalence of CH and its association with survival in a population of CS patients in a quaternary center.

METHODS

We compared the frequency of CH mutations among 341 CS patients and 345 ambulatory heart failure (HF) matched for age, sex, ejection fraction, and HF aetiology. The association of CH with survival and levels of circulating inflammatory cytokines was analysed.

RESULTS

We detected 266 CH mutations in 149 of 686 (22%) patients. CS patients had a higher prevalence of CH-related mutations than HF patients (OR 1.5; 95% CI 1.0-2.1, P=0.02) and was associated with decreased survival (30-days: HR 2.7; 95% CI 1.3-5.7, P=0.006; 90-days: HR 2.2; 95% CI 1.3-3.9, P=0.003; and 3-years: HR 1.7; 95% CI 1.1-2.8, P=0.01). TET2 or ASXL1 mutations were associated with lower survival in CS patients at all-time points (P≤0.03). CS patients with TET2 mutations had higher circulating levels of SCD40L, IFNγ, IL-4, and TNFα (P≤0.04), while those with ASXL1 mutations had decreased levels of CCL7 (P=0.03).

CONCLUSIONS

CS patients have high frequency of CH, notably mutations in TET2 and ASXL1. This was associated with reduced survival and dysregulation of circulating inflammatory cytokines in those CS patients with CH. This article is protected by copyright. All rights reserved.

Sudden cardiac death risk stratification in hypertrophic cardiomyopathy: discrepancies persist among guidelines

Background

Differing criteria have been provided on sudden cardiac death (SCD) risk stratification in hypertrophic cardiomyopathy (HCM) by current guidelines. Recently, AHA/ACC proposed an algorithm with novel clinical markers. It remains to be established the impact of this new approach.

Purpose

Evaluate the impact of the 2020 AHA/ACC guideline on the 2014 ESC and 2011 ACCF/AHA criteria regarding SCD risk assessment and primary prevention implantable cardioverter-defibrillator (ICD) in HCM.

Methods

The database of a HCM center non-referred cohort was accessed for SCD risk profile between March 2007 and March 2020. The agreement for primary prevention ICD recommendations among guidelines was assessed with the Cohen's and Fleiss' Kappa coefficient, P&lt;0.05. SCD or appropriate ICD shock were defined as the primary end-point.

Results

A total of 100 patients, age 60±13 years, 55 (55%) females, were followed by 5±3 years. The maximal left ventricular (LV) wall thickness was 18±4 mm, 38 (38%) patients showed a family history of SCD, 22 (22%) syncope, 6 (6%) ejection fraction ≤50%, 2 (2%) LV apical aneurysm, 1 (1%) massive LV hypertrophy, 26 (26%) non-sustained ventricular tachycardia, and 23 (23%) extensive late gadolinium enhancement. An ICD was placed in 17 (17%) patients. According to the 2020 AHA/ACC guideline, 57 (57%) patients met class IIa recommendation, 27 (27%) class IIb, and 16 (16%) class III. The 2014 ESC model classified 14 (14%) in class IIa, 18 (18%) in class IIb, and 68 (68%) in class III. The 2011 ACCF/AHA considered 66 (66%) in class IIa, 6 (6%) in class IIb, and 28 (28%) in class III. The Cohen's Kappa was 0.200 (95% CI 0.292–0.107), P=0.0005, between the 2020 AHA/ACC and the 2014 ESC, and 0.520 (95% CI 0.651–0.388), P=0.0005, between the North American approaches. The Fleiss' Kappa was 0.219 (95% CI 0.303–0.135) P=0.0005 among the three guidelines, whereas it reached 0.221 (95% CI 0.334–0.108) for class IIa, 0.244 (95% CI 0.357–0.131) for class IIb and 0.202 (95% CI 0.315–0.089) for class III, P=0.0005. Figure 1 shows the patient's reclassification with the new guideline. The primary end-points occurred in 7 (7%) patients in a median follow-up of 6 (17–0.4) years. All of them were classified as IIa with the 2011 ACCF/AHA guideline, but only 4 (4%) met this class under the 2020 AHA/ACC, and none in the 2014 ESC model.

Conclusion

A low agreement was found among guidelines, especially between the 2020 AHA/ACC and the 2014 ESC criteria. The North American systems differed moderately, but the new approach has reduced the cases in class IIa and III recommendation for primary prevention ICD. In contrast, the recent 2020 guideline has increased the number of patients in class IIa in relation to the European model, but both strategies have not protected the totality of patients with SCD or appropriate shock.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Hospital de Clínicas de Porto Alegre Figure 1

A Comprehensive and Contemporary Review on Immunosuppression Therapy for Heart Transplantation

Heart transplantation is the standard of therapy for patients with end-stage heart disease. Since the first human-to-human heart transplantation, performed in 1967, advances in organ donation, surgical techniques, organ preservation, perioperative care, immunologic risk assessment, immunosuppression agents, monitoring of graft function and surveillance of long-term complications have drastically increased recipient survival. However, there are yet many challenges in the modern era of heart transplantation in which immunosuppression may play a key role in further advances in the field. A fine-tuning of immune modulation to prevent graft rejection while avoiding side effects from over immunosuppression has been the vital goal of basic and clinical research. Individualization of drug choices and strategies, taking into account the recipient's clinical characteristics, underlying heart failure diagnosis, immunologic risk and comorbidities seem to be the ideal approaches to improve post-transplant morbidity and survival while preventing both rejection and complications of immunosuppression. The aim of the present review is to provide a practical, comprehensive overview of contemporary immunosuppression in heart transplantation. Clinical evidence for immunosuppressive drugs is reviewed and practical approaches are provided. Cardiac allograft rejection classification and up-to-date management are summarized. Expanding therapies, such as photophoresis, are outlined. Drug-to-drug interactions of immunosuppressive agents focused on cardiovascular medications are summarized. Special situations involving heart transplantation such as sarcoidosis, Chagas diseases and pediatric immunosuppression are also reviewed. The evolution of phamacogenomics to individualize immunosuppressive therapy is described. Finally, future perspectives in the field of immunosuppression in heart transplantation are highlighted.

Admission Bedside Lung Ultrasound Reclassifies Mortality Prediction in Patients With ST-Segment–Elevation Myocardial Infarction

Background:

Early risk stratification is essential for in-hospital management of ST-segment–elevation myocardial infarction. Acute heart failure confers a worse prognosis, and although lung ultrasound (LUS) is recommended as a first-line test to assess pulmonary congestion, it has never been tested in this setting. Our aim was to evaluate the prognostic ability of admission LUS in patients with ST-segment–elevation myocardial infarction.

Methods:

LUS protocol consisted of 8 scanning zones and was performed before primary percutaneous coronary intervention by an operator blinded to Killip classification. A LUS combined with Killip (LUCK) classification was developed. Receiver operating characteristic and net reclassification improvement analyses were performed to compare LUCK and Killip classifications.

Results:

We prospectively investigated 215 patients admitted with ST-segment–elevation myocardial infarction between April 2018 and June 2019. Absence of pulmonary congestion detected by LUS implied a negative predictive value for in-hospital mortality of 98.1% (93.1–99.5%). The area under the receiver operating characteristic curve of the LUCK classification for in-hospital mortality was 0.89 ( P =0.001), and of the Killip classification was 0.86 ( P <0.001; P =0.05 for the difference between curves). LUCK classification improved Killip ability to predict in-hospital mortality with a net reclassification improvement of 0.18.

Conclusions:

In a cohort of patients with ST-segment–elevation myocardial infarction undergoing primary percutaneous coronary intervention, admission LUS added to Killip classification was more sensitive than physical examination to identify patients at risk for in-hospital mortality. LUCK classification had a greater area under the receiver operating characteristic curve and reclassified Killip classification in 18% of cases. Moreover, absence of pulmonary congestion on LUS provided an excellent negative predictive value for in-hospital mortality.

Expanding benefits from cardiac resynchronization therapy to exercise-induced left bundle branch block in advanced heart failure

Indications of cardiac resynchronization therapy (CRT) do not include exercise‐induced left bundle branch block, but functional impairment could be improved with CRT in such cases. A 57‐year‐old woman with idiopathic dilated cardiomyopathy (ejection fraction 23%) presented with New York Heart Association Class IV and recurrent hospitalizations. During heart transplant evaluation, a new onset of intermittent left bundle branch block was observed on the cardiopulmonary exercise test. CRT was implanted, and 97% resynchronization rate was achieved. In 12 month follow‐up, both clinical and prognostic exercise parameters improved. In patients with heart failure with reduced ejection fraction and no left bundle branch block at rest, exercise test can uncover electromechanical dyssynchrony that may benefit from CRT.