Related Experiment Video

Updated: Apr 27, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
12:45

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

Published on: December 11, 2017

10.2K

PR interval identifies clinical response in patients with non-left bundle branch block: a Multicenter Automatic

Valentina Kutyifa1, Martin Stockburger2, James P Daubert2

  • 1From the University of Rochester Medical Center, NY (V.K., H.K., I.G., A.B., S.M., W.Z., A.J.M.); Experimental and Clinical Research Center, a Joint Cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine, Berlin, Germany (M.S.); Cardiology Department, Duke University, Durham, NC (J.P.D., F.H.); Department of Medicine, University of Iowa Health Care (B.O.); Henry Ford Hospital, Detroit, MI (C.S.); and Semmelweis University, Heart Center, Budapest, Hungary (B.M.). Valentina.Kutyifa@heart.rochester.edu.

Circulation. Arrhythmia and Electrophysiology
|June 26, 2014
PubMed

Insights

In patients without left bundle branch block (LBBB), a prolonged PR interval (≥230 ms) indicates a significant benefit from cardiac resynchronization therapy with defibrillator (CRT-D). However, normal PR intervals may suggest CRT-D is detrimental.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Medical Devices

Background:

  • Cardiac resynchronization therapy with defibrillator (CRT-D) showed no clinical benefit in Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) patients with non-left bundle branch block (non-LBBB).
  • The PR interval, a measure of atrioventricular conduction, was investigated as a potential modulator of CRT-D response in non-LBBB patients.

Purpose of the Study:

  • To investigate the association between baseline PR interval duration and clinical outcomes in non-LBBB patients treated with CRT-D.
  • To determine if PR interval subgroups modify the efficacy of CRT-D compared to implantable cardioverter-defibrillator (ICD) therapy.

Main Methods:

  • Analysis of 537 non-LBBB patients from the MADIT-CRT trial, categorized by baseline PR interval (<230 ms vs. ≥230 ms).
  • Primary endpoint: composite of heart failure or death. Secondary endpoints: heart failure events and all-cause mortality.
  • Cox proportional hazards regression models were used to compare CRT-D versus ICD therapy within PR interval subgroups.

Main Results:

  • Patients with prolonged PR interval (≥230 ms; n=96) experienced a 73% reduction in heart failure/death risk and an 81% reduction in all-cause mortality with CRT-D versus ICD.
  • Patients with normal PR interval (<230 ms; n=438) showed a trend towards increased heart failure/death risk (HR 1.45) and a >2-fold higher mortality risk (HR 2.14) with CRT-D versus ICD.
  • Significant interaction was observed between PR interval and treatment effect (P<0.001 for both primary and mortality endpoints).

Conclusions:

  • A prolonged baseline PR interval identifies non-LBBB patients who benefit significantly from CRT-D therapy.
  • In non-LBBB patients with a normal baseline PR interval, CRT-D implantation may be associated with adverse outcomes and potentially deleterious effects.
  • PR interval assessment could refine patient selection for CRT-D in the non-LBBB population.
Abstract

Keywords:
atrioventricular blockcardiac resynchronization therapydefibrillators, implantableheart failuremortality

More Related Videos

Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System10:17

Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System

Published on: April 11, 2025

2.3K
Programmed Electrical Stimulation in Mice07:29

Programmed Electrical Stimulation in Mice

Published on: May 26, 2010

20.3K

Related Concept Videos

Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...
786
Cardiac Action Potential01:30

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
11.5K
Electrocardiogram01:29

Electrocardiogram

An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...
9.4K
Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
13.4K
Electrocardiogram Fundamentals01:28

Electrocardiogram Fundamentals

Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin...
2.1K
Acute Coronary Syndrome III: Diagnostic Studies01:30

Acute Coronary Syndrome III: Diagnostic Studies

Diagnosing acute coronary syndrome or ACS begins with a thorough patient history. Notable symptoms include central, crushing chest pain radiating to the left arm, neck, jaw, or back, along with shortness of breath, sweating (diaphoresis), nausea, vomiting, dizziness, and palpitations.It is crucial to note any history of cardiac illnesses and assess risk factors, including age, gender, smoking, hypertension, diabetes, hyperlipidemia, and a sedentary lifestyle.During physical examination, vital...
493