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Related Concept Videos

Heart Failure Drugs: Inotropic Agents01:26

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Positive inotropic agents are commonly used as the first line of treatment for heart failure. One such agent is digoxin, derived from the genus Digitalis, which has been known for centuries but effectively utilized since 1785. However, these cardiac glycosides can have potentially toxic effects due to their mechanism of action, which involves inhibiting Na+/K+-ATPase and increasing contractility. Digoxin is absorbed orally and distributed in various tissues, including the CNS. It has a long...
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Introduction to AEDAn Automated External Defibrillator (AED) is a portable medical device that analyzes the heart's rhythm and, if necessary, delivers an electrical shock to help the heart re-establish an effective rhythm during sudden cardiac arrest (SCA). SCA occurs when the heart suddenly and unexpectedly stops beating, leading to a loss of blood flow to the brain and other vital organs. In such emergencies, time is of the essence, and using an AED, combined with Cardiopulmonary...
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Cardiomyopathy II: Dilated Cardiomyopathy01:30

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Dilated cardiomyopathy, or DCM, is a progressive myocardial disorder characterized by ventricular chamber dilation and contractile dysfunction.EtiologyVarious factors can cause DCM, including hypertension and heavy alcohol intake, which contribute to the weakening and enlargement of the heart muscle. Viral infections, such as Coxsackievirus B, adenoviruses, and influenza, can lead to DCM by causing inflammation and damage to heart tissue. Certain chemotherapeutic agents, including daunorubicin,...
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Pulse rhythm01:30

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Pulse rhythm refers to the pattern of pulsations within specific intervals, offering valuable insights into the regularity or irregularity of the heart's beats as observed through the pattern of pulsation within specific intervals. A regular pulse exhibits a consistent heart rate with uniform waveforms and pulsation force, variations of which can be classified as normal, weak, or bounding.
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Exercise and Cardiovascular Response01:20

Exercise and Cardiovascular Response

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Exercise significantly impacts cardiovascular response, which is crucial for understanding patient health and designing effective treatment plans.
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Regular physical activity is essential for maintaining cardiovascular health, with aerobic exercises being particularly effective. According to the American Heart Association, 150 minutes of moderate to intense aerobic exercise per week is recommended for a healthy heart. Aerobic activities may include brisk walking, running, bicycling, cross-country skiing, and swimming, ideally performed three to five times per week.
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Updated: Jul 12, 2025

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
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Cardiac resynchronization using fusion pacing during exercise.

Peregrine G Green1,2,3, Cristiana Monteiro2, David A Holdsworth1,3

  • 1Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, Oxford, UK.

Journal of Cardiovascular Electrophysiology
|October 27, 2023
PubMed
Summary
This summary is machine-generated.

Fusion pacing maintains optimal cardiac resynchronization therapy (CRT) timing during exercise. Optimizing QRS duration at rest improves exercise performance and cardiac efficiency in CRT patients.

Keywords:
exercisefusionheart failurepacingresynchronization

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Exercise Physiology

Background:

  • Fusion pacing in cardiac resynchronization therapy (CRT) requires precise timing between left ventricular and right ventricular activation.
  • It remains uncertain if this fusion pacing is maintained during exercise when atrioventricular (AV) conduction fluctuates.

Purpose of the Study:

  • To compare the efficacy of fusion pacing (SyncAV™ algorithm) versus fixed AV delays (AVD) during exercise in CRT patients using cardiopulmonary exercise testing (CPET).

Main Methods:

  • A double-blinded, randomized, crossover study involving 20 CRT patients with PR intervals < 250 ms.
  • Patients underwent two CPET tests: one with SyncAV™ and another with a fixed AVD of 120 ms, with other programming optimized for narrowest QRS duration (QRSd).

Main Results:

  • Both fusion pacing and fixed AVD resulted in similar QRSd narrowing at rest.
  • No significant differences were observed in peak oxygen consumption (V̇O₂ PEAK), anaerobic threshold (VT1), or time to reach these metrics between the two pacing modes.
  • However, programming that achieved the narrowest QRSd at rest led to significantly narrower QRSd during exercise, increased peak O₂ pulse (stroke volume surrogate), and improved cardiac efficiency.

Conclusions:

  • Fusion pacing is maintained during exercise in CRT patients without negatively impacting exercise capacity compared to fixed AVD.
  • Optimizing programming for the narrowest QRSd at rest is crucial for enhancing exercise QRSd, peak stroke volume, and overall cardiac efficiency.