In Vivo Cardiac Electrophysiology in Mice: Determination of Atrial and Ventricular Arrhythmic Substrates.

Cardiac arrhythmias are a common cardiac condition that might lead to fatal outcomes. A better understanding of the molecular and cellular basis of arrhythmia mechanisms is necessary for the development of better treatment modalities. To aid these efforts, various mouse models have been developed for studying cardiac arrhythmias. Both genetic and surgical mouse models are commonly used to assess the incidence and mechanisms of arrhythmias. Since spontaneous arrhythmias are uncommon in healthy young mice, intracardiac programmed electrical stimulation (PES) can be performed to assess the susceptibility to pacing-induced arrhythmias and uncover the possible presence of a proarrhythmogenic substrate. This procedure is performed by positioning an octopolar catheter inside the right atrium and ventricle of the heart through the right jugular vein. PES can provide insights into atrial and ventricular electrical activity and reveal whether atrial and/or ventricular arrhythmias are present or can be induced. Here, we explain detailed procedures used to perform this technique, possible troubleshooting scenarios, and methods to interpret the results obtained. © 2024 Wiley Periodicals LLC. Basic Protocol: Programmed electrical stimulation in mice.

Optical mapping and optogenetics in cardiac electrophysiology research and therapy: a state-of-the-art review.

State-of-the-art innovations in optical cardiac electrophysiology are significantly enhancing cardiac research. A potential leap into patient care is now on the horizon. Optical mapping, using fluorescent probes and high-speed cameras, offers detailed insights into cardiac activity and arrhythmias by analysing electrical signals, calcium dynamics, and metabolism. Optogenetics utilizes light-sensitive ion channels and pumps to realize contactless, cell-selective cardiac actuation for modelling arrhythmia, restoring sinus rhythm, and probing complex cell-cell interactions. The merging of optogenetics and optical mapping techniques for 'all-optical' electrophysiology marks a significant step forward. This combination allows for the contactless actuation and sensing of cardiac electrophysiology, offering unprecedented spatial-temporal resolution and control. Recent studies have performed all-optical imaging ex vivo and achieved reliable optogenetic pacing in vivo, narrowing the gap for clinical use. Progress in optical electrophysiology continues at pace. Advances in motion tracking methods are removing the necessity of motion uncoupling, a key limitation of optical mapping. Innovations in optoelectronics, including miniaturized, biocompatible illumination and circuitry, are enabling the creation of implantable cardiac pacemakers and defibrillators with optoelectrical closed-loop systems. Computational modelling and machine learning are emerging as pivotal tools in enhancing optical techniques, offering new avenues for analysing complex data and optimizing therapeutic strategies. However, key challenges remain including opsin delivery, real-time data processing, longevity, and chronic effects of optoelectronic devices. This review provides a comprehensive overview of recent advances in optical mapping and optogenetics and outlines the promising future of optics in reshaping cardiac electrophysiology and therapeutic strategies.

Effect of electroacupuncture at Neiguan (PC6) at different time points on myocardial ischemia reperfusion arrhythmia in rats.

OBJECTIVE: To observe the effects of electroacupuncture at Neiguan (PC6) at different time points on reperfusion arrhythmia (RA) after myocardial ischemia and reperfusion in rats, and to investigate the correlation of this protective effect with nerve growth factor (NGF), tyrosine kinase A (TrkA), tyrosine hydroxylase (TH), and norepinephrine (NE). METHODS：A total of 72 Sprague-Dawley male rats were randomly divided into six groups (n = 12 rats/group): normal group (Norm), sham operation group (Sham), ischemia reperfusion group (I/R), pre-ischemic electroacupuncture group (EAI), pre-reperfusion electroacupuncture group (EAII), post-reperfusion electroacupuncture group (EAIII). The myocardial ischemia-reperfusion injury (MIRI) model was induced by occlusion of left anterior descending coronary artery for 20 min followed by reperfusion for 40 min in rats. With no intervention in the Norm group and only threading without ligation in the Sham group. Electroacupuncture pre-treatment at 20 min/d for 7 d before ligation in the EAⅠ group, 20 min of electroacupuncture before reperfusion in the EAII group and 20 min of electroacupuncture after reperfusion in the EAIII group. The electrocardiogram (ECG) of each group was recorded throughout the whole process, and the success of the MIRI model was determined based on the changs of J-point and T-wave in the ECG. The arrhythmia score was used to record premature ventricular contractions, ventricular tachycardia and ventricular fibrillation during the reperfusion period to assess the reperfusion induced arrhythmias. The expression levels of NGF, TrkA, TH protein were measured by Western blot. Moreover, the expression levels of plasma and myocardial NE levels were detected by enzyme linked immunosorbent assay. RESULTS: The differences between Norm group and Sham group were not statistically significant in all indexes. Arrhythmia score, myocardial NGF, TrkA, TH, and NE expression were significantly higher in the I/R group compared with the Sham group. Arrhythmia score, myocardial NGF, TrkA, TH, and NE expression were significantly lower in each EA group compared with the I/R group. CONCLUSION: Electroacupuncture at Neiguan (PC6) at different time points can reduce the incidence and severity of reperfusion arrhythmias in rats. This protective effect is related to electroacupuncture regulating NGF, TrkA, TH, NE expression and reducing sympathetic hyperactivation.

Practical guidance to reduce radiation exposure in electrophysiology applying ultra low-dose protocols: a European Heart Rhythm Association review.

Interventional electrophysiology offers a great variety of treatment options to patients suffering from symptomatic cardiac arrhythmia. Catheter ablation of supraventricular and ventricular tachycardia has globally evolved a cornerstone in modern arrhythmia management. Complex interventional electrophysiological procedures engaging multiple ablation tools have been developed over the past decades. Fluoroscopy enabled interventional electrophysiologist throughout the years to gain profound knowledge on intracardiac anatomy and catheter movement inside the cardiac cavities and hence develop specific ablation approaches. However, the application of X-ray technologies imposes serious health risks to patients and operators. To reduce the use of fluoroscopy during interventional electrophysiological procedures to the possibly lowest degree and to establish an optimal protection of patients and operators in cases of fluoroscopy is the main goal of modern radiation management. The present manuscript gives an overview of possible strategies of fluoroscopy reduction and specific radiation protection strategies.

Evaluation of the effect of sodium zirconium cyclosilicate on arrhythmia-related cardiovascular outcomes in patients receiving chronic haemodialysis with hyperkalaemia: protocol for the multicentre, randomised, controlled DIALIZE-Outcomes study.

INTRODUCTION: Patients with kidney failure receiving chronic haemodialysis have elevated risk of arrhythmias potentially increasing the likelihood of sudden cardiac death, stroke and hospitalisation. The DIALIZE study (NCT03303521) demonstrated that sodium zirconium cyclosilicate (SZC) was an efficacious and well-tolerated treatment for predialysis hyperkalaemia in patients undergoing haemodialysis. The DIALIZE-Outcomes study evaluates the effect of SZC on sudden cardiac death and arrhythmia-related cardiovascular outcomes in patients receiving chronic haemodialysis with recurrent hyperkalaemia. METHODS AND ANALYSIS: International, multicentre, randomised, double-blind, placebo-controlled study conducted at 357 study sites across 25 countries. Adults (≥18 years) receiving chronic haemodialysis three times per week with recurrent predialysis serum potassium (K+) ≥5.5 mmol/L post long interdialytic interval (LIDI) are eligible. Patients (~2800) will be randomised 1:1 to SZC or placebo, starting at 5 g orally once daily on non-dialysis days and titrated weekly in 5 g increments (maximum 15 g) to target predialysis serum K+ 4.0-5.0 mmol/L post LIDI. The primary objective is to evaluate efficacy of SZC versus placebo in reducing occurrence of the primary composite endpoint of sudden cardiac death, stroke or arrhythmia-related hospitalisation, intervention or emergency department visit. Secondary endpoints include efficacy of SZC versus placebo in maintaining normokalaemia (serum K+ 4.0-5.5 mmol/L post LIDI) at the 12-month visit, preventing severe hyperkalaemia (serum K+ ≥6.5 mmol/L post LIDI) at the 12-month visit and reducing the incidence of individual cardiovascular outcomes. Safety of SZC will be evaluated. The study is event driven, with participants remaining in the study until 770 primary endpoint events have occurred. Average time in the study is expected to be ~25 months. ETHICS AND DISSEMINATION: Approval was obtained from the relevant institutional review board/independent ethics committee from each participating site (approving bodies in supplementary information). The results will be submitted to a peer-reviewed journal. TRIAL REGISTRATION NUMBERS: EudraCT 2020-005561-14 and clinicaltrials.gov identifier NCT04847232.

Efficacy of acupuncture combined with oral Chinese medicine in the treatment of arrhythmia: A meta-analysis.

BACKGROUND: At present, Western medicine treatment methods for arrhythmia emerge in an endless stream, but the accompanying side effects are also exposed, which brings pressure on medical resources and social economy. In recent years, the advantages of acupuncture combined with traditional Chinese medicine (TCM) in the control of arrhythmia have become increasingly prominent. Neiguan (PC6) is the collateral point in pericardium meridian; acupuncture at Neiguan can nourish the heart and calm the mind, and also plays an important role in treating arrhythmias. There is currently a lack of evidence-based medical evidence for the combination of acupuncture and TCM in the treatment of arrhythmia. This study aimed to investigate the effect of acupuncture combined with oral TCM in the treatment of arrhythmia. METHODS: Randomized controlled trials published from the inception of databases to June 2022 were reviewed by searching the PubMed, Cochrane Library, Embase, CNKI, VIP, and WanFang databases. Review Manager 5.4.1 was used for the meta-analysis after the reviewers scanned the literature, extracted information, and identified the risk of bias. RESULTS: Eleven randomized controlled trials with 804 patients were reviewed, including 402 and 402 patients in the treatment and control groups, respectively. The results of the meta-analysis showed a significant benefit of acupuncture plus oral TCM in terms of clinical effectiveness compared with oral TCM alone (n = 696; relative risk (RR), 1.22; 95% confidence interval (CI) 1.14 to 1.30; P < .00001) and in lowering the number of premature beats in 24 hours (n = 374; standard mean difference, -10,55; 95% confidence interval (95% CI) -14.61 to -6.49; P < .00001). Acupuncture plus oral TCM was also found to improve the conversion rate (n = 168; RR, 1.32; 95% CI, 1.14-1.52; P = .0002) and increase the left ventricular ejection fraction (n = 250; mean difference, 6.57; 95% CI, 4.11-9.04; P < .00001), but it had no significant increase in adverse events (n = 262; RR, 0.57; 95% CI 0.30-1.09; P = .09). CONCLUSION: Compared with oral TCM alone, acupuncture combined with oral TCM showed a clear benefit in treating arrhythmias and had no increase in adverse events.

[Intraoperative management of potentially fatal arrhythmias after anesthesia induced by severe hypokalemia: A case report].

Severe hypokalemia is defined as the concentration of serum potassium lower than 2.5 mmol/L, which may lead to serious arrhythmias and cause mortality. We report an unusual case of potentially fatal ventricular arrhythmias induced by severe hypokalemia in a patient undergoing laparoscopic partial nephrectomy in Peking University Third Hospital due to irregular use of indapamide before operation. Indapamide is a sulfonamide diuretic with vasodilative and calcium antagonistic effects, which enhances sodium delivery to the renal distal tubules resulting in a dose-related increase in urinary potassium excretion and decreases serum potassium concentrations. The electrolyte disorder caused by the diuretic is more likely to occur in the elderly patients, especially those with malnutrition or long-term fasting. Hence, the serum potassium concentration of the patients under indapamide therapy, especially elderly patients, should be monitored carefully. Meanwhile, the potassium concentration measured by arterial blood gas analysis is different from that measured by venous blood or laboratory test. According to the previous research, the concentration of potassium in venous blood was slightly higher than that in arterial blood, and the difference value was 0.1-0.5 mmol/L. This error should be taken into account when rapid intravenous potassium supplementation or reduction of blood potassium level was carried out clinically. In the correction of severe hypokalemia, the standard approach often did not work well for treating severe hypokalemia. The tailored rapid potassium supplementation strategy shortened the time of hypokalemia and was a safe and better treatment option to remedy life-threatening arrhythmias caused by severe hypokalemia with a high success rate. Through the anesthesia management of this case, we conclude that for the elderly patients who take indapamide or other potassium excretion diuretics, the electrolyte concentration and the general volume state of the patients should be comprehensively measured and fully evaluated before operation. It may be necessary for us to reexamine the serum electrolyte concentration before anesthesia induction on the morning of surgery in patients with the history of hypokalemia. For severe hypokalemia detected after anesthesia, central venous cannulation access for individualized rapid potassium supplementation is an effective approach to reverse the life-threatening arrhythmias caused by severe hypokalemia and ensure the safety of the patients.

Intraoperative management of potentially fatal arrhythmias after anesthesia induced by severe hypokalemia: A case report / 北京大学学报(医学版)

Severe hypokalemia is defined as the concentration of serum potassium lower than 2.5 mmol/L, which may lead to serious arrhythmias and cause mortality. We report an unusual case of potentially fatal ventricular arrhythmias induced by severe hypokalemia in a patient undergoing laparoscopic partial nephrectomy in Peking University Third Hospital due to irregular use of indapamide before operation. Indapamide is a sulfonamide diuretic with vasodilative and calcium antagonistic effects, which enhances sodium delivery to the renal distal tubules resulting in a dose-related increase in urinary potassium excretion and decreases serum potassium concentrations. The electrolyte disorder caused by the diuretic is more likely to occur in the elderly patients, especially those with malnutrition or long-term fasting. Hence, the serum potassium concentration of the patients under indapamide therapy, especially elderly patients, should be monitored carefully. Meanwhile, the potassium concentration measured by arterial blood gas analysis is different from that measured by venous blood or laboratory test. According to the previous research, the concentration of potassium in venous blood was slightly higher than that in arterial blood, and the difference value was 0.1-0.5 mmol/L. This error should be taken into account when rapid intravenous potassium supplementation or reduction of blood potassium level was carried out clinically. In the correction of severe hypokalemia, the standard approach often did not work well for treating severe hypokalemia. The tailored rapid potassium supplementation strategy shortened the time of hypokalemia and was a safe and better treatment option to remedy life-threatening arrhythmias caused by severe hypokalemia with a high success rate. Through the anesthesia management of this case, we conclude that for the elderly patients who take indapamide or other potassium excretion diuretics, the electrolyte concentration and the general volume state of the patients should be comprehensively measured and fully evaluated before operation. It may be necessary for us to reexamine the serum electrolyte concentration before anesthesia induction on the morning of surgery in patients with the history of hypokalemia. For severe hypokalemia detected after anesthesia, central venous cannulation access for individualized rapid potassium supplementation is an effective approach to reverse the life-threatening arrhythmias caused by severe hypokalemia and ensure the safety of the patients.

[Heavy metal! A case of severe iron overload and supraventricular arrhythmias in a thalassemia major patient]. / Heavy metal! Un caso di severo accumulo di ferro e aritmie sopraventricolari in paziente con talassemia major.

Cardiovascular complications are among the main causes of mortality and morbidity in patients with thalassemia major. Iron-chelation therapy is essential to prevent the chronic iron overload linked to the need for transfusions and the consequent cardiac hemosiderosis. Despite the wide use of iron-chelation drugs, today it is still possible to find cases of severe iron accumulation. Furthermore, even regardless of iron overload and cardiac dysfunction, the thalassemic patient has a high arrhythmic burden, especially for supraventricular arrhythmias. There are still many doubts and open questions about the management of such patients, especially regarding the correct use of anticoagulant therapy and the best utilization of therapeutic strategies available for rhythm control. The case presented shows how the interventional approach with catheter ablation can be useful also in the acute phase when antiarrhythmic drugs are ineffective and it is not possible to wait for the iron-chelation therapy to take effect.

Ventricular Arrhythmias in Seniors with Heart Failure: Present Dilemmas and Therapeutic Considerations: A Systematic Review.

BACKGROUND: Heart Failure (HF) is a global public health problem, which affects over 23 million people worldwide. The prevalence of HF is higher among seniors in the USA and other developed countries. Ventricular Arrhythmias (VAs) account for 50% of deaths among patients with HF. We aim to elucidate the factors associated with VAs among seniors with HF, as well as therapies that may improve the outcomes. METHODS: PubMed, Web of Science, Scopus, Cochrane Library databases, Science Direct, and Google Scholar were searched using specific keywords. The reference lists of relevant articles were searched for additional studies related to HF and VAs among seniors as well as associated outcomes. RESULTS: The prevalence of VAs increases with worsening HF. A 24-hour Holter electrocardiogram may be useful in risk stratifying patients for device therapy if they do not meet the criterion of low ventricular ejection fraction. Implantable Cardiac Defibrillators (ICDs) are superior to anti-arrhythmic drugs in reducing mortality in patients with HF. Guideline-Directed Medical Therapy (GDMT) together with device therapy may be required to reduce symptoms. In general, the proportion of seniors on GDMT is low. A combination of ICDs and cardiac resynchronization therapy may improve outcomes in selected patients. CONCLUSION: Seniors with HF and VAs have high mortality even with the use of device therapy and GDMT. The holistic effect of device therapy on outcomes among seniors with HF is equivocal. More studies focused on seniors with advanced HF as well as therapeutic options are, therefore, required.

Shared Decision Making in Cardiac Electrophysiology Procedures and Arrhythmia Management.

Shared decision making (SDM) has been advocated to improve patient care, patient decision acceptance, patient-provider communication, patient motivation, adherence, and patient reported outcomes. Documentation of SDM is endorsed in several society guidelines and is a condition of reimbursement for selected cardiovascular and cardiac arrhythmia procedures. However, many clinicians argue that SDM already occurs with clinical encounter discussions or the process of obtaining informed consent and note the additional imposed workload of using and documenting decision aids without validated tools or evidence that they improve clinical outcomes. In reality, SDM is a process and can be done without decision tools, although the process may be variable. Also, SDM advocates counter that the low-risk process of SDM need not be held to the high bar of demonstrating clinical benefit and that increasing the quality of decision making should be sufficient. Our review leverages a multidisciplinary group of experts in cardiology, cardiac electrophysiology, epidemiology, and SDM, as well as a patient advocate. Our goal is to examine and assess SDM methodology, tools, and available evidence on outcomes in patients with heart rhythm disorders to help determine the value of SDM, assess its possible impact on electrophysiological procedures and cardiac arrhythmia management, better inform regulatory requirements, and identify gaps in knowledge and future needs.

Efficacy on rabbits with arrhythmia: needling acupoint of Neiguan (PC6) at shallow or deep depth, and retaining needles for 10, 20, or 30 min.

OBJECTIVE: To compare the effects of Neiguan (PC6) acupuncture at different depths and retention time on arrhythmia duration, myocardial tissue morphology, mRNA expression level of L-type calcium channel α1C subunit and Ca2 + -Mg2 + -AtPase activity in tachirrhythmia model of rabbits. METHODS: The tachyarrhythmia model was made by intravenous injection of barium chloride into the ears of rabbits. A total of 56 healthy adult male New Zealand big-eared white rabbits, apply the random number table method, divided into normal control group (group A), model group (group B), shallow needling Neiguan (PC6) 10 min group (group C), shallow needling Neiguan (PC6) 20 min group (group D), shallow needling Neiguan (PC6) 30 min group (group E), deep needling Neiguan (PC6) 10 min group (group F), deep needling Neiguan (PC6) 20 min group (group G), deep needling Neiguan (PC6) 30 min group (group H), 7 animals in each group. Electrocardiograms were used to collect the duration of arrhythmia; hematoxylin-eosin staining method was performed on myocardial tissue, RT-PCR tested the expression of α1C subunit mRNA, and the activity of Ca2 + -Mg2 + -ATPase were quantified by phosphorus determination method. RESULTS: The duration of arrhythmia in each acupuncture treatment group was shortened to varying degrees. Compare to the model group, the tissue damage from barium chloride inducing was improved in the acupuncture group. Compared to the model group, except for group E, most treatment groups had varying degrees of improvement with significantly down-regulated L-type calcium channel α1C subunit mRNA expressions level and increased Ca2+ -Mg2+ -ATPase activity. CONCLUSIONS: The effect of acupuncture at Neiguan (PC6) with different depths and retention time can reduce the duration of arrhythmia induced by barium chloride relatively, improve the induced pathological changes, down regulate L-type calcium channel α1C subunit mRNA expressions level and increase Ca2 + -Mg2 + -ATPase activity. Both the shallow and deep tissues of Neiguan (PC6) may be involved in transmitting acupuncture information. There is an optimal induction period for shallow needling at Neiguan (PC6) to reach the best therapeutic effect.

Long-Term, Single-Centre Observation of Patients with Cardiac Implantable Electronic Devices.

Background and Objectives: Electrotherapy is a valuable treatment method for patients with heart rhythm disturbances. There are very few observations of long-term patients treated with these techniques. There is a particular lack of this type of study conducted in Eastern European countries. The aim of this single-centre analysis was to evaluate the long-term survival (from 2010 to 2018) of patients treated with electrotherapy devices, taking into account clinical factors facilitating the prognosis of these patients. Materials and Methods: The patients (N = 2071) subsequently included in the study were subjected to the implementation or replacement of cardiac pacemakers. The medical records of all the patients were analysed. Data concerning death, made available by the State Systems Department of the Ministry of Administration and Digitization, were used. Results: The patients with VVI pacemakers had the worst prognosis after the replacement of the devices. Male patients had a worse prognosis, regardless of the kind of device implanted. Advanced atrioventricular conduction disturbances, chronic kidney disease, and hypothyroidism with reduced left ventricular ejection fraction were among the most significant coexisting diseases. Conclusions: The long-term prognosis of patients under different forms of electrotherapy remains poor. Despite the more straightforward technique, a single-chamber device (VVI/AAI) or generator replacement leads to the worst prognosis. The complexity of the clinical picture that stems from coexisting diseases and advanced age is of the utmost importance.

How common are non-acute coronary syndrome (ACS) diagnoses in patients with suspected ACS investigated with coronary angiography in New Zealand? (ANZACS-QI 58).

BACKGROUND AND AIMS: The last two decades in New Zealand have seen increased availability of primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) and early invasive coronary angiography (ICA) for other high-risk acute coronary syndrome (ACS) patients. One metric to assess the clinical appropriateness of these invasive strategies is to examine the false-positive rate for the investigation (ie, the rate of non-ACS diagnoses). METHODS: All patients presenting to New Zealand public hospitals with suspected ACS who underwent ICA between 2015 and 2019 were recorded prospectively in the All New Zealand Acute Coronary Syndrome Quality Improvement registry. The cohort was divided according to clinical impression at presentation: (1) suspected STEMI <24h and (2) other suspected ACS. The final discharge diagnosis for each patient were obtained from the registry. RESULTS: There were 6,059 (20%) patients with suspected STEMI <24h and 24,258 (80%) with other suspected ACS. Of the suspected STEMIs <24h, 90.6% had a final diagnosis of STEMI, 3.5% non-ST segment elevation ACS (NSTEACS) and only 5.9% had a non-ACS diagnosis. Of those with other suspected ACS, 80.7% had a final ACS diagnosis. Across all New Zealand district health boards (DHBs), the proportion of non-ACS diagnoses was similar for suspected STEMI presentations. However, for other suspected ACS, the proportions were higher in DHBs with rapid access to coronary interventional facilities than in those without (17.6% vs 7.0%, p<0.001). CONCLUSIONS: False-positive catheter laboratory activations for suspected STEMI patients are low across New Zealand. The differences in the proportion of non-ACS diagnoses according to DHB interventional capability for other suspected ACS requires further investigation.

[Lifestyle changes for stroke prevention]. / Schlaganfallprävention durch Lifestyle-Modifikation.

Changes of lifestyle have a substantial effect on stroke prevention, especially in high-risk patients. Maintaining a healthier lifestyle can have greater effects than most pharmacological therapies of cardiovascular prevention. For example, increasing the amount of physical activity, adopting a healthy diet, limiting alcohol consumption and quitting smoking are associated with a 70 % decrease in stroke risk. Despite the abundance of observational data and meta-analyses assessing the association of different lifestyle changes and stroke risk, the literature frequently lacks evidence from randomized controlled clinical trial. This article will provide an overview of various forms of lifestyle changes and summarize their potential to modify the risk of stroke.

An electrographic AV optimization for the maximum integrative atrioventricular and ventricular resynchronization in CRT.

BACKGROUND: Atrioventricular (AV) delay could affect AV and ventricular synchrony in cardiac resynchronization therapy (CRT). Strategies to optimize AV delay according to optimal AV synchrony (AVopt-AV) or ventricular synchrony (AVopt-V) would potentially be discordant. This study aimed to explore a new AV delay optimization algorithm guided by electrograms to obtain the maximum integrative effects of AV and ventricular resynchronization (opt-AV). METHODS: Forty-nine patients with CRT were enrolled. AVopt-AV was measured through the Ritter method. AVopt-V was obtained by yielding the narrowest QRS. The opt-AV was considered to be AVopt-AV or AVopt-V when their difference was < 20 ms, and to be the AV delay with the maximal aortic velocity-time integral between AVopt-AV and AVopt-V when their difference was > 20 ms. RESULTS: The results showed that sensing/pacing AVopt-AV (SAVopt-AV/PAVopt-AV) were correlated with atrial activation time (Pend-As/Pend-Ap) (P < 0.05). Sensing/pacing AVopt-V (SAVopt-V/PAVopt-V) was correlated with the intrinsic AV conduction time (As-Vs/Ap-Vs) (P < 0.01). The percentages of patients with more than 20 ms differences between SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V were 62.9% and 57.1%, respectively. Among them, opt-AV was linearly correlated with SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V. The sensing opt-AV (opt-SAV) = 0.1 × SAVopt-AV + 0.4 × SAVopt-V + 70 ms (R2 = 0.665, P < 0.01) and the pacing opt-AV (opt-PAV) = 0.25 × PAVopt-AV + 0.5 × PAVopt-V + 30 ms (R2 = 0.560, P < 0.01). CONCLUSION: The SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V were correlated with the atrial activation time and the intrinsic AV conduction interval respectively. Almost half of the patients had a > 20 ms difference between SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V. The opt-AV could be estimated based on electrogram parameters.