A shorter R wave peak time in left bundle branch pacing may not be a marker of more physiological ventricular activation: A case report.

Left bundle branch pacing (LBBp) is a promising alternative to conventional biventricular pacing cardiac resynchronization therapy. The left anterior fascicle (LAF) is adjacent to the left ventricular outflow tract, while the left posterior fascicle (LPF) dominates a broader area of the left ventricle. Whether LAF or LPF dominates ventricular activation has not been determined. We present the case of a 76-year-old man who underwent LBBp implantation and propose the left ventricular activation domination in LPF pacing, an alternative when LBBp is unavailable.

Septal scar as a barrier to left bundle branch area pacing.

BACKGROUND: The use of left bundle branch area pacing (LBBAP) for bradycardia pacing and cardiac resynchronization is increasing, but implants are not always successful. We prospectively studied consecutive patients to determine whether septal scar contributes to implant failure. METHODS: Patients scheduled for bradycardia pacing or cardiac resynchronization therapy were prospectively enrolled. Recruited patients underwent preprocedural scar assessment by cardiac MRI with late gadolinium enhancement imaging. LBBAP was attempted using a lumenless lead (Medtronic 3830) via a transeptal approach. RESULTS: Thirty-five patients were recruited: 29 male, mean age 68 years, 10 ischemic, and 16 non-ischemic cardiomyopathy. Pacing indication was bradycardia in 26% and cardiac resynchronization in 74%. The lead was successfully deployed to the left ventricular septum in 30/35 (86%) and unsuccessful in the remaining 5/35 (14%). Septal late gadolinium enhancement was significantly less extensive in patients where left septal lead deployment was successful, compared those where it was unsuccessful (median 8%, IQR 2%-18% vs. median 54%, IQR 53%-57%, p < .001). CONCLUSIONS: The presence of septal scar appears to make it more challenging to deploy a lead to the left ventricular septum via the transeptal route. Additional implant tools or alternative approaches may be required in patients with extensive septal scar.

R wave peak time and no reflow following primary percutaneous coronary intervention: Immediate and short-term outcomes.

BACKGROUND: No reflow (NR) remains an important constraint in management of ST elevation myocardial Infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI). Most ECG parameters validated till date including ST resolution are postprocedural. R wave peak time (RWPT) is a dynamic parameter and reflects conduction delay in ischaemic myocardium in selected leads supplied by infarct related artery (IRA). The present study was undertaken to see whether preprocedural RWPT per se or RWPT following primary PCI can predict persistence of NR along with immediate and short-term clinical outcome. METHODS: 200 patients were enrolled after exclusion. Clinical, Biochemical, ECG parameters including RPWT and angiographic parameters (pre- and post-procedure) were recorded. ECG papers was analysed using digital image processing software (http://imagej.nih.gov/ij/). All patients were followed up for 6 months. RESULTS: NR was observed in 35% of the patients. Age, Diabetes, symptom to balloon time, higher thrombus burden, peak CPK-MB level (pre and post procedure) were significantly higher in NR group. On ECG analysis, baseline RWPT, QRS duration and pathological Q wave were significantly higher in NR group. On multivariate analysis, age (OR 1.10 CI 1.00-1.21 P = 0.04), thrombus grade ≥ 3 in IRA (OR 12.38 CI 2.08-73.58 P = 0.006), symptom to balloon time (OR 2.18 CI 1.6-3.0 P < 0.001) and baseline RWPT on ECG [OR 1.86 CI 1.24-2.78, P = 0.003] were found to be independent predictors of NR. Increase in RWPT following primary PCI was found to both highly sensitive and specific for diagnosing persistence of NR after primary PCI. Follow up at the end of 6 months has shown that patients with increased RWPT following primary PCI had worse short-term cardiovascular outcomes compared to those with decreased RWPT following primary PCI. CONCLUSION: Baseline RWPT is a significant predictor of NR in patients of STEMI undergoing primary PCI. A persistently increased RWPT following primary PCI is also a highly sensitive and specific ECG marker of persistence of NR which is associated with adverse short-term clinical outcome.

The Predictive Value of R Wave Peak Time to Detect Thrombus Burden in St-segment Elevation Myocardial Infarction: A Retrospective Cohort Study in a Tertiary Medical Center.

UNASSIGNED: Background: Patients with higher thrombus burden have higher procedural complications and more long-term adverse cardiac events. Detecting patients with high thrombus burden (HTB) before coronary intervention could help avoid procedural complications. Objective: The research aimed to analyze the R wave peak time (RWPT) on the electrocardiogram to predict thrombus burden before coronary angiography in patients with acute ST-segment elevation myocardial infarction (STEMI). Materials and Methods: A total of 159 patients with STEMI were included in the study conducted at a tertiary medical center. The thrombolysis in myocardial infarction (TIMI) thrombus scale was applied to assess the thrombus burden. TIMI thrombus grades 0, 1, 2, and 3 were accepted as low; 4 and 5 had HTB. RWPT was measured from the beginning of the QRS complex to the R-peak from the leads pointing to the infarct-related artery. Results: Patients were divided into two groups according to their angiographically defined thrombus burden as low and high. The low thrombus burden group (LTB) comprised fifty-four patients, whereas the HTB group comprised 105 patients. In the LTB group, RWPT was 47.96 ± 9.17 ms, and in the HTB group was 53.58 ± 8.92 ms; it was significantly longer (p < 0.01). Receiver operating characteristic analysis showed that a cut-off value of preprocedural RWPT of > 46.5 ms predicted the occurrence of HTB with a sensitivity and specificity of 87.62% and 51.85%, respectively (AUC 0.682, 95% CI 0.590-0.774, p < 0.001). Conclusion: The present study evaluated the relationship between the RWPT and thrombus burden in STEMI patients. Based on the results, RWPT is an independent predictor of HTB.

Delayed intrinsicoid deflection: Electrocardiographic harbinger of heart disease.

Delayed intrinsicoid deflection (DID) is an emerging electrocardiogram (ECG) marker of major clinical significance that is increasingly getting attention. Intrinsicoid deflection measures ventricular depolarization in the initial portion of the QRS complex, and DID is defined as an R wave peak time of ≥50 ms in leads V5 and V6 . Prior studies have identified an independent association between DID and cardiovascular conditions such as left ventricular hypertrophy, heart failure, and sudden cardiac death. The exact mechanism that results in DID remains unknown. Animal models indicate that DID may result from abnormal calcium and potassium conductance as well as extracellular matrix remodeling. DID remains an ECG marker of interest given its potential predictive value of underlying cardiovascular pathology and adverse events. This review provides an update on the proposed mechanisms and associations, as well as the clinical and research implications of DID.

The association between electrocardiographic R wave peak time and coronary artery disease severity in patients with non-ST segment elevation myocardial infarction and unstable angina pectoris.

BACKGROUND: We aimed to evaluate possible association between QRS duration (QRSD), R wave peak time (RWPT), and coronary artery disease severity identified using the SYNTAX score (SS) in patients with unstable angina pectoris (USAP) or non-ST segment elevation myocardial infarction (NSTEMI). METHOD: A total of 176 USAP/NSTEMI patients were enrolled in the study. RESULTS: The high SS group (>22, n:45) patients had a higher prevalence of diabetes mellitus (DM); presence of ST segment depression ≥0.5 mm and 1 mm; ST segment elevation in the AVR lead (AVRSTE); longer QRSD and RWPT; and lower left ventricular ejection fraction (LVEF) than the low SS group (≤22, n: 131). The LVEF, AVRSTE, and RWPT (OR: 1.035, 95% CI: 1.003-1.067; p = 0.030) were independent predictors of high SS. CONCLUSION: The present study demonstrated that RWPT and AVRSTE could be used as predictors of high SS.

R-Peak Time: An Electrocardiographic Parameter with Multiple Clinical Applications.

In the 12-lead electrocardiogram (ECG), the time from the onset of the QRS complex (Q or R wave) to the apex or peak of R or to R' (when present), using indirect or semidirect surface unipolar precordial leads, bipolar limb leads or unipolar limb leads, is called ventricular activation time (VAT), R wave peak time (RWPT), R-peak time or intrinsicoid deflection (ID). The R-peak time in a specific ECG lead is the interval from the earliest onset of the QRS complex, preferably determined from multiple simultaneously recorded leads, to the peak (maximum) of the R wave or R' if present. Irrespective of the relative height of the R and R' waves, the R-peak time is measured to the second peak. The parameter corresponds to the time of the electrical activation occurring from the endocardium to the epicardium as reflected by the recording electrode located at a variable distance on the body surface, depending on the lead type: a unipolar precordial lead, a bipolar or unipolar limb lead. In normal conditions, the R-peak time for the thinner-walled right ventricle is measured from lead V1 or V2 and its upper limit of normal is 35 ms. The R-peak time for the left ventricle (LV) is measured from leads V5 to V6 and 45 ms is considered the upper limit of normal. In this manuscript, we review the clinical applications of this parameter.

An individualized criterion for left bundle branch capture in patients with a narrow QRS complex.

BACKGROUND: Left bundle branch (LBB) pacing (LBBP) is a physiological pacing; however, the accuracy of current electrocardiographic criteria for LBBP remains inadequate. OBJECTIVE: The purpose of this study was to establish a novel individualized criterion to improve the accuracy of LBBP determination in patients with a narrow QRS complex. METHODS: Patients in whom both LBBP and left ventricular septal pacing (LVSP) were acquired during operation were enrolled. LBB conduction time (LBBCT) was measured from LBB potential (LBBpo) to intrinsic QRS onset. LBBpo-V6RWPT, Native-V6RWPT, and Paced-V6RWPT were respectively measured from LBBpo, intrinsic QRS onset, and stimulus to R-wave peak in V6. ΔV6RWPT was the difference value between Paced-V6RWPT and Native-V6RWPT. The accuracy of ΔV6RWPT criterion for determining LBBP was evaluated. RESULTS: In all 71 enrolled patients, ΔV6RWPT was <30 ms during LBBP (21.3 ± 4.6 ms; range 9.3-28.3 ms) but was >30 ms during LVSP (38.5 ± 4.6 ms; range 31.1-47.0 ms). The probability distribution of ΔV6RWPT was well separated between LBBP and LVSP. Sensitivity and specificity of the novel criterion of "ΔV6RWPT <30 ms" for determining LBBP both were 100%. However, the optimal cutoff value of Paced-V6RWPT for validation of LBBP was 64.2 ms, and sensitivity and specificity were 84.5% and 97.2%, respectively. Paced-V6RWPT during LBBP was equivalent to LBBpo-V6RWPT in all patients. There was a strong linear correlation between Native-V6RWPT and LBBpo-V6RWPT (r = 0.796; P <.001). CONCLUSION: ΔV6RWPT could be an accurate individualized criterion for determining LBB capture with high sensitivity and specificity and was superior over the fixed Paced-V6RWPT criterion.

Electrocardiographic predictors of clinical outcomes in nonischemic cardiomyopathy patients with left bundle branch area pacing cardiac resynchronization therapy.

BACKGROUND: Paced QRS morphology may vary during left bundle branch area pacing (LBBAP) per the pacing location. It remains unclear whether electrocardiographic changes observed during LBBAP can predict clinical outcomes. OBJECTIVE: We aimed to assess correlation between characteristics of paced QRS on the electrocardiogram and clinical outcomes in heart failure patients with nonischemic cardiomyopathy. METHODS: Of 79 consecutive heart failure patients receiving LBBAP, 59 patients were included in this prospective study after exclusions. LBBAP was performed using Medtronic 3830 lead. Patients were assigned to various groups on the basis of paced QRS morphology in lead V1 (qR and Qr), QRS axis (normal, left, or right), and V6 R-wave peak time (RWPT, ≤80 ms or >80 ms) to compare echocardiographic outcomes. RESULTS: RWPT was significantly shorter (75.7 ± 17.5 ms vs 85.3 ± 11.3 ms; P = .014), transition during threshold testing was more commonly observed (81.5% vs 53%; P = .02), and improvement in left ventricular ejection fraction (LVEF) was significantly greater in the qR group (21.4% ± 6.4% vs 16.4% ± 8.3%; P = .013) compared with the Qr group. RWPT or LVEF did not differ in patients with different paced QRS axis (P > .05). Whereas qR morphology and presence of transition during threshold testing independently predicted LVEF improvement, RWPT lacked predictive value. Nonresponders had greater incidence of loss of R' (P = .009) and prolonged RWPT (P = .003) on follow-up compared with average responders and superresponders. CONCLUSION: Paced qR morphology and transition during threshold testing predicted greater improvement in LVEF, whereas RWPT lacked predictive value. Loss of terminal R in lead V1 and prolongation of RWPT on follow-up prognosticated nonresponse to LBBAP.

Physiologic Differentiation Between Selective His Bundle, Nonselective His Bundle and Septal Pacing.

His bundle (HB) pacing is an increasingly popular method of physiologic ventricular pacing. The electrocardiographic hallmark of physiologic pacing is the preservation or restoration of physiologic activation times in the left ventricle-a principle of paramount diagnostic importance. The current review focuses on the differentiation between 3 possible capture types when the pacing lead is placed in the HB region: selective HB capture when only HB is activated, nonselective HB capture when there is simultaneous activation of the adjacent right ventricular septal (RVS) myocardium, and selective RVS capture when HB is not activated at all but only septal myocardium.

Evaluation of Criteria for Left Bundle Branch Capture.

Left bundle branch pacing (LBBP) provides electrical and mechanical synchrony at low and stable pacing output and effectively corrects distal conduction system disease. The criteria for differentiating LBBP from LV septal pacing has not been validated in large trials. There are several electrocardiography-based and intracardiac electrogram-based criteria to confirm LBB capture. In this section, the authors review these criteria and their overall accuracy.

R-peak time in clinically healthy dogs with different thoracic conformations.

R-peak time (RPT) is an electrocardiographic parameter that represents the time taken for electrical activation to spread from the endocardium to the epicardium. In human medicine, right ventricular RPT is measured from lead V1 to lead V2, and left ventricular RPT from lead V5 to lead V6. The aim of the present study was to define RPT duration in a group of clinically healthy dogs with different thoracic conformations. Sixty clinically healthy dogs underwent a 12-lead electrocardiogram recorded using a previously described precordial system. The dogs were allocated into three morphologic groups. In the brachymorphic group, the median and 25th-75th percentiles for RPT in V1 were 10.5 ms (10-12 ms); V2, 18 ms (16.5-20 ms); V3, 19 ms (18-22 ms); V4, 20 ms (17-23.5 ms); V5, 21 ms (18.5-24 ms); and V6: 22 ms (18.5-25.5 ms). In the mesomorphic group, RPT in V1 was 16 ms (14-18 ms); V2, 22 ms (20-24 ms); V3, 23 ms (21-25 ms); V4, 23 ms (22-25 ms); V5, 25 ms (23-27 ms); and V6, 28 ms (25-30 ms). In the dolichomorphic group, RPT in V1 was 15 ms (13-17 ms); V2, 29 ms (26-32.5 ms); V3, 30 ms (27-33.5 ms); V4, 29.5 ms (26-35 ms); V5, 30 ms (28-34 ms); and V6, 31.5 ms (28-35 ms). RPT in V1 was significantly shorter than RPT in V2 to V6 in all morphotypes (P < 0.05). In all precordial leads, RPT was significantly different between morphotypes (P < 0.05). These results are in agreement with previous findings in humans and with the observation that V1 reads the right ventricle and V2 to V6 read the left ventricle. These preliminary data provide RPT ranges in clinically healthy dogs of different morphotypes.

Physiology-based electrocardiographic criteria for left bundle branch capture.

BACKGROUND: During left bundle branch (LBB) area pacing, it is important to confirm that capture of the LBB, and not just capture of only adjacent left ventricular (LV) myocardium, has been achieved. OBJECTIVE: The purpose of this study was to establish electrocardiographic (ECG) criteria for LBB capture. We hypothesized that because LBB pacing results in physiological depolarization of the LV, then the native QRS can serve as a reference for diagnosis of LBB capture in the same patient. METHODS: Only patients with evidence of LBB capture (QRS morphology transition) were included. Several QRS characteristics were compared between the native rhythm and different types of LBB area capture. RESULTS: A total of 357 ECGs (124 patients) were analyzed: 118 with native rhythm, 124 with nonselective LBB capture, 69 with selective LBB capture, and 46 with LV septal capture. Our hypotheses that during LBB capture the paced V6 R-wave peak time (RWPT; measured from QRS onset) equals the native V6 RWPT and that the paced V6 RWPT (measured from the stimulus) equals the LBB potential to V6 R-wave peak interval were positively validated. Criteria based on these rules had sensitivity and specificity of 88.2%-98.0% and 85.7%-95.4%, respectively. Moreover, 100% specific V6 RWPT cutoff for LBB capture diagnosis in patients with narrow QRS/right bundle branch block was determined to be 74 ms. CONCLUSION: We showed equivalency of LV activation times on ECG during native and paced LBB conduction. Therefore, if V6 RWPT is longer during pacing, this finding is indicative of lack of LBB capture.

The relationship between R wave peak time and left ventricular mass index in patients with end-stage renal disease on hemodialysis.

PURPOSE: Cardiovascular complications have been reported to be the main cause of mortality in patients with end-stage renal disease (ESRD). Although left ventricular hypertrophy is the most common clinical presentation of cardiac remodeling, cardiovascular complications may also include disturbances of the heart conduction system. The R wave peak time (RWPT) has been previously associated with left ventricular hypertrophy and myocardial ischemia. In this study, we aimed to investigate the relationship between RWPT and echocardiographic parameters in patients with ESRD. METHODS: This study enrolled 66 patients (29 females, age 57.2 ± 12.8 years) with ESRD, and 72 controls (37 females, age 55.3 ± 10.1 years) with similar risk factors. All patients underwent electrocardiography and transthoracic echocardiography. The RWPT was defined as the interval between the onset of the QRS complex and the peak of the R or R' wave. RESULTS: There was no significant difference in terms of clinical and demographic parameters between ESRD patients and controls. Left ventricular ejection fraction was similar between the groups. However, left atrial diameter, interventricular septal thickness, posterior wall thickness, left ventricular mass (LVM) and left ventricular mass index (LVMI) were significantly higher in patients with ESRD. Among electrocardiographic parameters, P wave and QRS complex durations and RWPT were significantly higher in patients with ESRD. Prolonged RWPT, increased LVM and LVMI were identified as associates of ESRD. Furthermore, RWPT correlated well with LVM and LVMI. CONCLUSION: The present study demonstrated that RWPT prolonged significantly in patients with ESRD. Furthermore, prolonged RWPT has been associated with increased LVM and LVMI.

The Predictive Value of R Wave Peak Time to Detect Thrombus Burden in St-segment Elevation Myocardial Infarction: A Retrospective Cohort Study in a Tertiary Medical Center

Abstract Background: Patients with higher thrombus burden have higher procedural complications and more long-term adverse cardiac events. Detecting patients with high thrombus burden (HTB) before coronary intervention could help avoid procedural complications. Objective: The research aimed to analyze the R wave peak time (RWPT) on the electrocardiogram to predict thrombus burden before coronary angiography in patients with acute ST-segment elevation myocardial infarction (STEMI). Materials and Methods: A total of 159 patients with STEMI were included in the study conducted at a tertiary medical center. The thrombolysis in myocardial infarction (TIMI) thrombus scale was applied to assess the thrombus burden. TIMI thrombus grades 0, 1, 2, and 3 were accepted as low; 4 and 5 had HTB. RWPT was measured from the beginning of the QRS complex to the R-peak from the leads pointing to the infarct-related artery. Results: Patients were divided into two groups according to their angiographically defined thrombus burden as low and high. The low thrombus burden group (LTB) comprised fifty-four patients, whereas the HTB group comprised 105 patients. In the LTB group, RWPT was 47.96 ± 9.17 ms, and in the HTB group was 53.58 ± 8.92 ms; it was significantly longer (p < 0.01). Receiver operating characteristic analysis showed that a cut-off value of preprocedural RWPT of > 46.5 ms predicted the occurrence of HTB with a sensitivity and specificity of 87.62% and 51.85%, respectively (AUC 0.682, 95% CI 0.590-0.774, p < 0.001). Conclusion: The present study evaluated the relationship between the RWPT and thrombus burden in STEMI patients. Based on the results, RWPT is an independent predictor of HTB.

Specificity of electrocardiographic criteria for the differential diagnosis of wide QRS complex tachycardia in patients with intraventricular conduction defect.

BACKGROUND: In patients with organic intraventricular conduction defects (IVCDs), (1) QRS morphology during sinus rhythm frequently meets ventricular tachycardia (VT) morphological criteria and (2) there are further rate-related changes in QRS morphology. OBJECTIVE: To search for the best morphological criteria in this context. METHODS: We prospectively studied 69 patients, in sinus rhythm, with QRS duration ≥120 ms. Continuous rapid atrial pacing (RAP) trains were introduced at increasing rates in order to mimic supraventricular tachycardia. We analyzed the specificity of VT criteria during RAP. Finally, we used the criteria with a specificity of ≥0.9 in a "test sample" of 53 patients with preexisting IVCD and wide complex tachycardia to confirm their validity. RESULTS: Only 10 of the 20 analyzed criteria had a specificity of ≥0.9 during RAP at the highest rate. The specificity of these 10 criteria was confirmed in the test sample. The best accuracy to diagnose VT was obtained: for an isolated criterion: "R-wave peak time (RWPT) ≥50 ms at lead II" (specificity = 0.97; sensitivity = 0.67); for an algorithm: the combination of 2 criteria "RWPT ≥50 ms at lead II" and "absence of RS patterns in precordial leads" (specificity = 0.97; sensitivity = 0.88). CONCLUSIONS: In patients with IVCD, (1) specificity of most VT criteria is low during RAP, suggesting a limited applicability of many of these criteria in case they develop supraventricular tachycardia, and (2) the superior accuracy to diagnose VT was observed with "RWPT ≥50 ms at lead II" and for an algorithm with the combination of "RWPT ≥50 ms at lead II" and "absence of RS patterns in precordial leads."