Paced QRS morphology mimicking complete left bundle branch block induced by right ventricular pacing is associated with pacing-induced cardiomyopathy.

INTRODUCTION: Right ventricular (RV) pacing sometimes causes left ventricular (LV) systolic dysfunction, also known as pacing-induced cardiomyopathy (PICM). However, the association between specifically paced QRS morphology and PICM development has not been elucidated. This study aimed to investigate the association between paced QRS mimicking a complete left bundle branch block (CLBBB) and PICM development. METHODS: We retrospectively screened 2009 patients who underwent pacemaker implantation from 2010 to 2020 in seven institutions. Patients who received pacemakers for an advanced atrioventricular block or bradycardia with atrial fibrillation, baseline LV ejection fraction (LVEF) ≥ 50%, and echocardiogram recorded at least 6 months postimplantation were included. The paced QRS recorded immediately after implantation was analyzed. A CLBBB-like paced QRS was defined as meeting the CLBBB criteria of the American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society in 2009. PICM was defined as a ≥10% LVEF decrease, resulting in an LVEF of <50%. RESULTS: Among the 270 patients analyzed, PICM was observed in 38. Baseline LVEF was lower in patients with PICM, and CLBBB-like paced QRS was frequently observed in PICM. Multivariate analysis revealed that low baseline LVEF (odds ratio [OR]: 0.93 per 1% increase, 95% confidence interval [CI]: 0.89-0.98, p = 0.006) and CLBBB-like paced QRS (OR: 2.69, 95% CI: 1.25-5.76, p = 0.011) were significantly associated with PICM development. CONCLUSION: CLBBB-like paced QRS may be a novel risk factor for PICM. RV pacing, which causes CLBBB-like QRS morphology, may need to be avoided, and patients with CLBBB-like paced QRS should be followed-up carefully.

Predictors for new-onset conduction block in patients with pure native aortic regurgitation after transcatheter aortic valve replacement with a new-generation self-expanding valve (VitaFlow Liberty™): a retrospective cohort study.

BACKGROUND: New-generation self-expanding valves can improve the success rate of transcatheter aortic valve replacement (TAVR) for severe pure native aortic regurgitation (PNAR). However, predictors of new-onset conduction block post-TAVR using new-generation self-expanding valves in patients with PNAR remain to be established. Therefore, this study aimed to identify predictors of new-onset conduction block post-TAVR using new-generation self-expanding valves (VitaFlow Liberty™) in patients with PNAR. METHODS: In this retrospective cohort study, patients were categorized into pacemaker and non-pacemaker groups based on their need for new postoperative permanent pacemaker implantation (PPI). Based on the postoperative presence of either new-onset complete left bundle branch block (cLBBB) or high-grade atrioventricular block (AVB), patients were further classified into conduction disorder and non-conduction disorder groups. Laboratory, echocardiographic, computed tomography, preoperative and postoperative electrocardiography, and procedural and clinical data were collected immediately after TAVR and during hospitalization and compared between the groups. Multivariate logistic regression analysis was performed incorporating the significant variables from the univariate analyses. RESULTS: This study examined 68 consecutive patients with severe PNAR who underwent TAVR. In 20 patients, a permanent pacemaker was fitted postoperatively. Multivariate logistic regression analysis revealed an association between the need for postoperative PPI and preoperative complete right bundle branch block (cRBBB) or first-degree AVB, as well as a non-tubular left ventricular outflow tract (LVOT). In addition, valve implantation depth and angle of aortic root were independent predictors of new-onset cLBBB or high-grade AVB developing post-TAVR. The predictive value of valve implantation depth and angle of aortic root was further supported by receiver operating characteristic curve analysis results. CONCLUSIONS: In patients with PNAR undergoing TAVR using self-expanding valves, preoperative cRBBB or first-degree AVB and a non-tubular LVOT were indicators of a higher likelihood of PPI requirement. Moreover, deeper valve implantation depth and greater angle of aortic root may be independent risk factors for new-onset cLBBB or high-grade AVB post-TAVR. Valve implantation depth and angle of aortic root values may be used to predict the possibility of new cLBBB or high-grade AVB post-TAVR.

Left ventricular pacing in the treatment of pediatric cardiac dysfunction caused by idiopathic complete left bundle branch block.

OBJECTIVE: This study aimed to investigate the feasibility and effectiveness of transthoracic epicardial dual-chamber pacemaker implantation in the treatment of cardiac dysfunction caused by idiopathic complete left bundle branch block (CLBBB) in children. METHODS: Nine children diagnosed with cardiac dysfunction due to idiopathic CLBBB were included in this study. All patients underwent transthoracic epicardial dual-chamber pacemaker implantation. Cardiac function was evaluated using echocardiography during the follow-up. Additionally, intraventricular synchronization parameters were assessed using two-dimensional speckle tracking echocardiography (STE). RESULTS: Nine children (mean age, 3.0 ± 2.6 years) were included in this study. The median follow-up duration was 2 (interquartile range, 1-3) years. The cardiac function of all patients recovered to normal levels within 1 year postoperatively. The postoperative QRS duration on electrocardiography (142 ± 21 ms) was significantly shorter than that at baseline (106 ± 12 ms) (p < .05). Cardiac dyssynchrony in patients who manifested preoperatively achieved complete correction after pacemaker implantation. The comparison of preoperative and postoperative (last follow-up visit) synchronization parameters were as follows: longitudinal standard deviation of the time to peak strain, 99.0 ± 41.9 versus 36.8 ± 5.0 ms (p = .004); delay time of peak longitudinal strain, 252.2 ± 131.4 versus 35.0 ± 22.9 ms (p = .002); and longitudinal systolic dyssynchrony index, 2.8 ± 0.8% versus 1.0 ± 0.3% (p = .001), respectively. CONCLUSION: Transthoracic epicardial dual-chamber pacemaker implantation (with left atrial sensing and left ventricular single-site pacing) can be used for the treatment of cardiac dysfunction caused by idiopathic CLBBB in children.

Long-term outcomes of left bundle branch area pacing versus biventricular pacing in patients with heart failure and complete left bundle branch block.

Left bundle branch area pacing (LBBAP) has developed in an effort to improve cardiac resynchronization therapy (CRT). We aimed to compare the long-term clinical outcomes between LBBAP and biventricular pacing (BIVP) in patients with heart failure (HF) and complete left bundle branch block (CLBBB). Consecutive patients with HF and CLBBB requiring CRT received either LBBAP or BIVP were recruited at the Second Affiliated Hospital of Nanchang University from February 2018 to May 2019. We assessed their implant parameters, electrocardiogram (ECG), clinical outcomes at implant and during follow-up at 1, 3, 6, 12, and 24 months. Forty-one patients recruited including 21 for LBBAP and 20 for BIVP. Mean follow-up duration was 23.71 ± 4.44 months. LBBAP produced lower pacing thresholds, shorter procedure time and fluoroscopy duration compared to BIVP. The QRS duration was significantly narrower after LBBAP than BIVP (129.29 ± 31.46 vs. 156.85 ± 26.37 ms, p = 0.005). Notably, both LBBAP and BIVP significantly improved LVEF, LVEDD, NYHA class, and BNP compared with baseline. However, LBBAP significantly lowered BNP compared with BIVP (416.69 ± 411.39 vs. 96.07 ± 788.71 pg/ml, p = 0.007) from baseline to 24-month follow-up. Moreover, patients who received LBBAP exhibited lower number of hospitalizations than those in the BIVP group (p = 0.019). In addition, we found that patients with moderately prolonged left ventricular activation time (LVAT) and QRS notching in limb leads in baseline ECG respond better to LBBAP for CLBBB correction. LBBAP might be a relative safe and effective resynchronization therapy and as a supplement to BIVP for patients with HF and CLBBB.

Progression of incomplete toward complete left bundle branch block: A clinical and electrocardiographic analysis.

BACKGROUND: Complete left bundle branch block (cLBBB) is associated with increased cardiovascular mortality and heart failure. On the contrary, the clinical relevance of incomplete left bundle branch block (iLBBB) is less known. This study investigated the profile and outcome of iLBBB patients and assessed the risk of progression to cLBBB. METHODS: Patients diagnosed with iLBBB between July 2013 and April 2018 were retrospectively included. Subsequently, echo- and electrocardiographic examinations at time of iLBBB diagnosis and during follow-up, as well as progression to non-strict cLBBB and strict cLBBB, were evaluated. RESULTS: The study enrolled 321 patients (33% female, age 74 ± 11 years). During the follow-up of 21 (8;34) months, 33% of iLBBB patients evolved to non-strict cLBBB and 27% to strict cLBBB. iLBBB patients who evolved to non-strict or strict cLBBB were older, had more frequently reduced left ventricular ejection fraction, and had more often QRS notching/slurring in the lateral leads and inferior leads, compared to patients without progression to cLBBB. In multivariate analysis, only QRS notching/slurring in the lateral leads was independently associated with progression to non-strict cLBBB (odds ratio 4.64, p < .001) and strict cLBBB (odds ratio 9.6, p < .001). iLBBB patients with QRS notching/slurring had a progression rate to non-strict cLBBB of 52% and 49% to strict cLBBB. CONCLUSION: Among patients with iLBBB, up to one third of the patients progress to cLBBB within a period of 2 years. The presence of QRS notching/slurring in the lateral leads during iLBBB was the strongest predictor for progression toward cLBBB.

Postsystolic index for distinguishing coronary artery disease in left bundle branch block.

BACKGROUND: Left bundle branch block (LBBB) is associated with a high risk of death, particularly from ventricular tachyarrhythmia and myocardial infarction. It is difficult to clinically differentiate between ischemic and nonischemic LBBB. In this study, we investigated whether advanced echocardiographic variables, such as strain delay index (SDI) and postsystolic index (PSI), can be used to distinguish coronary artery disease (CAD) in patients with LBBB. METHODS: Our study included 102 patients with LBBB. All patients underwent echocardiography. The left ventricular ejection fraction (LVEF), left ventricular mass, PSI, SDI, global longitudinal strain (GLS), and time-to-peak longitudinal strain were then calculated. Coronary angiography was performed, and the patients were divided into groups with significant CAD and without significant CAD. RESULTS: Patients in the group with significant CAD were older than the patients in the group without significant CAD. The group had a higher prevalence of diabetes mellitus, hypertension, hyperlipidemia, and family history of CAD than the group without significant CAD. The group with significant CAD also had lower LVEF and GLS than the group without significant CAD. The group without significant CAD showed a direct correlation between LVEF and SDI and an inverse correlation between LVEF and PSI: P value = 0.040 and r = 0.255, and P value = 0.001 and r = -0.427, respectively. However, the group with significant CAD did not show any significant correlation between LVEF and SDI or PSI. CONCLUSION: Strain delay index and PSI may be useful markers in distinguishing CAD in patients with LBBB and preserved LVEF.

[Time course of changes in left ventricular twist in the presence of idiopathic left bundle branch block during exercise testing]. / Dinamika skruchivaniia levogo zheludochka pri idiopaticheskoi blokade levoi nozhki puchka Gisa vo vremia nagruzochnoi proby.

AIM: To investigate left ventricular (LV) deformation properties, rotation, and twist during a bicycle ergometer exercise test among patients with idiopathic left bundle branch block (LBBB). SUBJECTS AND METHODS: Thirty-four patients with idiopathic LBBB having a mean QRS duration of 153±24 msec were examined. A control group included 18 apparently healthy volunteers. All the patients and apparently healthy individuals underwent echocardiography to determine LV hemodynamic parameters, deformity, rotation and twist at rest and after exercise test. RESULTS: As compared with the control, the idiopathic LBBB group at rest showed decreases in LV global longitudinal deformity (-15.6±4.7 and -18.4±3.1%, respectively; p=0.037), apical rotation (4.59±4.2° and 8.99±3.68°; p=0.0067) and twist (9.08±4.59° and 13.96±4.61°; p=0.0156), whereas there were no differences in LV ejection fraction and end-systolic and end-diastolic volumes. After exercise testing there were no augmentations in basal and apical rotation and resulting ΔTwist in the idiopathic LBBB group compared with the control (-2.05±8.35 and 4.66±8.49%; p=0.0463). The described changes in LV rotation and twist during exercise testing occurred in the presence of elevated pulmonary artery systolic pressure (PASP) in the LBBB group compared with the control (41.6±3.81 and 32.4±3.81 mm Hg, respectively; p=0.0201). CONCLUSION: Decreases in LV basal, apical and resulting twist may lead to elevated PASP in patients with idiopathic LBBB during exercise.

Risk of mortality associated to chronic kidney disease in patients with complete left bundle branch block.

Chronic kidney disease (CKD) is associated with cardiac conduction defects and is a strong risk factor for heart failure. Complete left bundle branch block (cLBBB), a cardiac conduction abnormality, may have an unfavorable effect on ventricular mechanical synchrony and lead to the progression of heart failure. Once heart failure develops, it seems to act together with underlying CKD in a vicious circle. Therefore, this study aimed to explore the influence of CKD in patients with cLBBB by assessing the estimated glomerular filtration rate (eGFR). We examined a hospital-based sample of 416 adult patients with cLBBB from 2010 to 2013. The eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Cox proportional hazard models were used to estimate the hazard ratio for all-cause mortality and cardiovascular mortality. A total of 416 adult patients with a mean age of 71 ± 13 years were enrolled. The median follow-up period was 3.6 years. After adjusting for clinical, electrocardiographic parameters, and medication use, cox regression analysis showed that total mortality was significantly associated with older age (Hazard Ratio (HR) = 1.03, 95% CI = 1.01-1.05, p = 0.002), presence of congestive heart failure (HR = 2.39, 95% CI = 1.63-3.49, p < 0.001), advanced CKD (HR = 2.48, 95% CI = 1.71-3.59, p < 0.001), higher HR (HR = 1.02, 95% CI = 1.01-1.03, p < 0.001) and without use of ACEI/ARB (HR = 0.59, 95% CI = 0.41-0.85, p = 0.005) were independent predictors of the total mortality. Multivariate Cox hazard regression analysis demonstrated that, in comparison to patients lacking cLBBB, the coexistence of CKD (eGFR < 60 mL/min/1.73 m2) among those with LBBB significantly heightened the risks of both total mortality (HR ratio of 5.01 vs. 2.40) and CV death (HR ratio of 61.78 vs. 14.41) even following adjustment for clinical covariates and ECG parameters. In summary, within patients exhibiting cLBBB, the presence of CKD serves as a significant risk factor for all-cause mortality.

Treatment strategy for heart failure complicated with complete left bundle branch block and atrial tachycardia: a case report.

BACKGROUND: For patients with heart failure combined with complete left bundle branch block, cardiac resynchronization therapy is an important therapeutic method. If these patients also have atrial tachycardia, how to choose a treatment strategy deserves discussion. CASE PRESENTATION: A Chinese woman in her early 70s was admitted due to recurrent episodes of chest distress and asthma for 1 year. Physical and laboratory examinations showed filling of the jugular vein, lung rales, left enlargement of the heart boundary, edema of the lower limbs and elevation of N-terminal pro b-type natriuretic peptide. An electrocardiogram showed atrial tachycardia and a left bundle branch block. An echocardiography revealed enlargement of the left ventricle and left ventricular systolic dysfunction. After obtaining informed consent, the treatment strategy decided upon by the team was to use biventricular cardiac resynchronization therapy treatment and to not intervene for the atrial tachycardia, with left bundle branch area pacing as a backup. Due to twisted and narrow coronary vein branches, traditional biventricular pacing failed, and then, left bundle branch area pacing was attempted successfully. A follow-up echocardiography at 1 year showed improved systolic function. The outcomes for this patient are favorable, but the choice of interventional strategy is worthy of discussion in this case. CONCLUSION: For patients with heart failure combined with left bundle branch block and atrial tachycardia, left bundle branch area pacing can replace traditional biventricular pacing for cardiac resynchronization therapy treatment, and the therapeutic effect is significant. However, multiple factors need to be considered when formulating strategies, including whether there is bundle branch block under sinus rhythm, the success and recurrence rate of atrial tachycardia ablation, the response of cardiac resynchronization therapy, the costs of different strategies, and instrument implantation issues.

Reversible T-wave inversions during left bundle branch area pacing.

BACKGROUND: Our clinical observation found that T-wave inversions (TWIs) appeared during left bundle branch area pacing (LBBAP); however, the incidence and influencing factors were unclear. The study aimed to investigate the effects of LBBAP on T-wave and explore possible factors associated with TWIs. METHODS: This was a retrospective cohort study. An electrocardiogram (ECG) was acquired at baseline and after LBBAP. Baseline characteristics, ECG parameters, LBBAP parameters, and troponin T (TnT) levels were compared between the non-TWIs and TWIs groups. Multivariable logistic analyses were performed to adjust for potential confounders to identify the predictive factors of TWIs during LBBAP. RESULTS: A total of 398 consecutive patients who underwent successful LBBAP were assessed for inclusion between May 2017 and Jan 2021, and 264 (66.3%) patients had TWIs. The mean (standard deviation [SD]) baseline QRS duration (QRSd) was longer in the TWIs group compared to the non-TWIs group (125.9 [34.5] ms vs. 98.2 [18.1] ms; P <0.001). Multivariable logistic regression analysis suggested that QRSd >120 ms was an independent predictor for TWIs. TWIs were partially or com-pletely recovered in 151/172 (87.8%) patients during follow-up, the median (interquartile range [IQR]) follow-up duration was 10 days (7 days to 5.5 months). TWIs in patients with complete left bundle branch block (CLBBB) occurred more frequently in inferior wall leads (II, III, and aVF) and anterior wall leads (V1-V4) (P <0.05). Patients with complete right bundle branch block (CRBBB) were more prone to TWIs in high lateral wall leads (I and aVL) (P <0.05). There were no significant differences in TnT levels between the TWIs and non-TWIs groups. CONCLUSIONS: TWIs during LBBAP were clinically frequent and recoverable. QRSd >120 ms was independently associated with TWIs.

True complete left bundle branch block reveals dyssynchrony evaluated by semiconductor single-photon emission computed tomography.

BACKGROUND: Conventional complete left bundle branch block (CLBBB) criteria sometimes result in a false-positive diagnosis that does not represent dyssynchrony. Recently, true CLBBB criteria have been proposed to detect responders to cardiac resynchronization therapy (CRT), although their correlation with severity of dyssynchrony or natural prognosis is unclear. METHODS: Ninety-four consecutive patients (74 ± 9 years, 63 men) with conventional CLBBB during sinus rhythm underwent semiconductor SPECT. They were divided into two groups: patients with true CLBBB and others. True CLBBB was characterized by the mid-QRS notching/slurring and wide QRS duration (male, ≥140 milliseconds; female, ≥130 milliseconds). Multivariate analysis was performed to detect left ventricular dyssynchrony (LVD), defined as bandwidth ≥145° and/or phase standard deviation (SD) ≥43°. Primary endpoints (hospitalization for heart failure or cardiac death) were evaluated. RESULTS: True CLBBB had wider bandwidth (145 ± 83° vs 110 ± 64°, P = 0.024) and higher phase SD (48 ± 26° vs 35 ± 19°, P = 0.007). Ejection fraction (EF), end-diastolic volume (EDV), summed rest score (SRS), and the presence of ischemic heart disease (IHD) showed no differences between groups (P = 0.401, 0.591, 0.165, and 0.212, respectively). Multivariate analysis revealed that true CLBBB, EF, and EDV were significant predictors of LVD (odds ratio, 12.6, 0.90, 1.03; P = 0.003, 0.002, 0.022, respectively). At 3-year follow-up (median 667 days), primary endpoints were comparable in both groups (log-rank, P = 0.92). CONCLUSIONS: Patients with true CLBBB had more severe dyssynchrony on single-photon emission computed tomography than patients with nontrue CLBBB. On the other hand, the two groups showed no differences in EF, EDV, the presence of IHD, hospitalization for heart failure, and cardiac death.

Narrowing of the QRS complex, elimination of late gadolinium enhancement and remarkable reverse remodeling achieved by optimal medical treatment in non-ischemic dilated cardiomyopathy.

A 67-year-old woman presented with exertional dyspnea. An electrocardiogram showed complete left bundle branch block. Cardiac magnetic resonance imaging revealed left ventricular (LV) dilatation with reduced ejection fraction, no evidence of myocardial ischemia and late gadolinium enhancement (LGE) in the inferior LV wall. She was diagnosed with decompensated heart failure (HF) secondary to non-ischemic dilated cardiomyopathy. Narrowing of the QRS complex, disappearance of LGE, and remarkable LV reverse remodeling along with improvement in HF symptoms were achieved by combination therapy with angiotensin II receptor blocker, beta-blocker, and mineralocorticoid receptor antagonist. This case highlights the role of triple-blockade therapy in the treatment of HF. .

[Intermittent left bundle branch block - reversal to normal conduction during general anesthesia]. / Bloqueio intermitente de ramo esquerdo ­ reversão para condução normal durante anestesia geral.

BACKGROUND AND OBJECTIVES: Transient changes in intraoperative cardiac conduction are uncommon. Rare cases of the development or remission of complete left bundle branch block under general and locoregional anesthesia associated with myocardial ischemia, hypertension, tachycardia, and drugs have been reported. Complete left bundle branch block is an important clinical manifestation in some chronic hypertensive patients, which may also be a sign of coronary artery disease, aortic valve disease, or underlying cardiomyopathy. Although usually permanent, it can occur intermittently depending on heart rate (when heart rate exceeds a certain critical value). CASE REPORT: This is a case of complete left bundle branch block recorded in the preoperative period of urgent surgery that reverted to normal intraoperative conduction under general anesthesia after a decrease in heart rate. It resurfaced, intermittently and in a heart-rate-dependent manner, in the early postoperative period, eventually reverting to normal conduction in a sustained manner during semi-intensive unit monitoring. The test to identify markers of cardiac muscle necrosis was negative. Pain due to the emergency surgical condition and in the early postoperative period may have been the cause of the increase in heart rate up to the critical value, causing blockage. CONCLUSIONS: Although the development or remission of this blockade under anesthesia is uncommon, the anesthesiologist should be alert to the possibility of its occurrence. It may be benign; however, the correct diagnosis is very important. The electrocardiographic manifestations may mask or be confused with myocardial ischemia, factors that are especially important in a patient under general anesthesia unable to report the characteristic symptoms of ischemia.

Cardiac memory-induced T wave change during complete atrioventricular block in a patient with inferior acute myocardial infarction.

Cardiac memory is an electrocardiographic manifestation of transient T wave abnormalities, which is observed after abrupt interruption of abnormal ventricular activation. We report a case with preexisting complete left bundle branch block in whom cardiac memory was induced. This cardiac memory was induced by normalization of QRS morphology after development of complete atrioventricular block due to acute inferior myocardial infarction. .

Intermittent left bundle branch block - reversal to normal conduction during general anesthesia / Bloqueio intermitente de ramo esquerdo - reversão para condução normal durante anestesia geral

Abstract Background and objectives: Transient changes in intraoperative cardiac conduction are uncommon. Rare cases of the development or remission of complete left bundle branch block under general and locoregional anesthesia associated with myocardial ischemia, hypertension, tachycardia, and drugs have been reported. Complete left bundle branch block is an important clinical manifestation in some chronic hypertensive patients, which may also be a sign of coronary artery disease, aortic valve disease, or underlying cardiomyopathy. Although usually permanent, it can occur intermittently depending on heart rate (when heart rate exceeds a certain critical value). Case report: This is a case of complete left bundle branch block recorded in the preoperative period of urgent surgery that reverted to normal intraoperative conduction under general anesthesia after a decrease in heart rate. It resurfaced, intermittently and in a heart-rate-dependent manner, in the early postoperative period, eventually reverting to normal conduction in a sustained manner during semi-intensive unit monitoring. The test to identify markers of cardiac muscle necrosis was negative. Pain due to the emergency surgical condition and in the early postoperative period may have been the cause of the increase in heart rate up to the critical value, causing blockage. Conclusions: Although the development or remission of this blockade under anesthesia is uncommon, the anesthesiologist should be alert to the possibility of its occurrence. It may be benign; however, the correct diagnosis is very important. The electrocardiographic manifestations may mask or be confused with myocardial ischemia, factors that are especially important in a patient under general anesthesia unable to report the characteristic symptoms of ischemia.

Resumo Justificativa e objetivos: Alterações transitórias da condução cardíaca no intraoperatório são pouco frequentes. Foram reportados raros casos de desenvolvimento ou remissão de bloqueio completo de ramo esquerdo sob anestesia (geral e locorregional), associados a isquemia do miocárdio, hipertensão, taquicardia e fármacos. O bloqueio completo de ramo esquerdo é uma manifestação clínica importante em alguns hipertensos crônicos, pode também significar doença arterial coronária, doença valvular aórtica ou cardiomiopatia subjacentes. Embora habitualmente permanente, pode ocorrer na forma intermitente dependente da frequência cardíaca (quando a frequência cardíaca excede determinado valor crítico). Relato de caso: Este é um caso de bloqueio completo de ramo esquerdo registrado no pré-operatório de cirurgia urgente que reverteu para condução normal no intraoperatório sob anestesia geral após diminuição da frequência cardíaca. Ressurgiu, de forma intermitente e dependente da frequência cardíaca, no pós-operatório imediato, acabou por reverter novamente à condução normal de forma sustentada durante vigilância em unidade semi-intensiva. O estudo com marcadores de necrose muscular cardíacos foi negativo. A dor do quadro cirúrgico urgente e pós-operatório imediato pode ter estado na origem da subida da frequência cardíaca até ao valor crítico e causado bloqueio. Conclusões: Embora o desenvolvimento ou a remissão desse bloqueio sob anestesia sejam incomuns, o anestesiologista deverá estar alertado para a possibilidade da sua ocorrência. Pode ter caráter benigno, contudo o diagnóstico correto é muito importante. As manifestações eletrocardiográficas podem ser confundidas com ou encobrir isquemia miocárdica, fatos de especial importância num paciente sob anestesia geral incapaz de referir sintomatologia característica de isquemia.