Background: A rapid change in length of cardiac muscle during isometric contraction is followed by developed force that is less than appropriate for the new length because of deactivation of the contractile system. Length change deactivation may have favorable or unfavorable effects on cardiac function, depending on the circumstances under which it is produced.
Methods: Left ventricular papillary muscles from male Sprague-Dawley rats were arranged for recording of isometric force. After each control or reference isometric contraction, a quick release-quick stretch V-step was applied to the following contraction. For each repetition of control and experimental contractions, the time of application of V-steps was increased by 20 ms until peak force was reached. Effects of these V-steps were assessed from ratios of peak redeveloped force to peak force in an isometric reference contraction. Slopes of plots of these ratios versus time after the onset of the contraction were used to quantify the effects of inotropic agents on deactivation.
Results: Increasing calcium from 2.5 to 5.0 or 7.5 mM increased force by 12+/-4% (mean+/-SEM), did not change time to peak, and did not significantly alter the deactivation slope. Adding 5 mM epinephrine increased force by 16+/-5%, decreased time to peak by 34+/-3%, and increased the deactivation slope by 106+/-9% (P<0.001). Caffeine had variable effects on peak force, increased time to peak by 47+/-4%, and decreased the deactivation slope by 71+/-5% (P<0.001).
Conclusions: The quantitatively different effects of the three agents on length change deactivation slopes and time to peak force suggest a common mechanism, probably involving thin-filament cooperativity.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.2310/6650.2002.33519 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
A Scoping Review of Factors Associated with Delayed Extubation in Post Cardiac Surgery Patients.
Vasc Health Risk Manag
January 2025
Department of Critical Care and Emergency Nursing, Faculty of Nursing, Universitas Padjadjaran, Sumedang, West Java, Indonesia.
Background: Delayed extubation (DE) after cardiac surgery is associated with high morbidity, mortality, increased length of stay in the intensive care unit, and hospital costs. Various studies have identified factors that influence the occurrence of DE in patients after cardiac surgery, but no review has systematically synthesized the results.
Purpose: This review aimed to identify the influencing factors and the leading causes of DE in patients after cardiac surgery.
Impact of Preventive Intravenous Amiodarone on Reperfusion Ventricular Fibrillation in Patients With Left Ventricular Hypertrophy Undergoing Open-Heart Surgery: Randomized Controlled Clinical Trial.
JMIR Form Res
January 2025
Department of Anesthesiology and Perioperative Medicine, The First Affiliated Hospital of Nanjing Medical University, No. 300 Guangzhou Road, Nanjing, 210029, China, 86 2568303569.
Background: Ventricular fibrillation (VF) is a vicious arrhythmia usually generated after removal of the aortic cross-clamp (ACC) in patients undergoing open-heart surgery, which could damage cardiomyocytes, especially in patients with left ventricular hypertrophy (LVH). Amiodarone has the prominent properties of converting VF and restoring sinus rhythm. However, few studies concentrated on the effect of amiodarone before ACC release on reducing VF in patients with LVH.
View Article and Find Full Text PDFEchocardiographic phenotypes of diabetic myocardial disorder: evolution over 15 months follow-up in the ARISE-HF trial.
Cardiovasc Diabetol
January 2025
Cardiology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
Background: Diabetic myocardial disorder (DbMD, evidenced by abnormal echocardiography or cardiac biomarkers) is a form of stage B heart failure (SBHF) at high risk for progression to overt HF. SBHF is defined by abnormal LV morphology and function and/or abnormal cardiac biomarker concentrations.
Objective: To compare the evolution of four DbMD groups based on biomarkers alone, systolic and diastolic dysfunction alone, or their combination.
A combination of low-temperature radiofrequency thermocoagulation and pulsed radiofrequency of the bilateral Gasserian ganglion for bilateral trigeminal neuralgia due to multiple sclerosis: a case report.
JA Clin Rep
January 2025
Department of Pain Clinic, NTT Medical Center Tokyo, 5-9-22 Higashi-Gotanda, Shinagawa-Ku, Tokyo, 141-8625, Japan.
Background: Bilateral trigeminal neuralgia secondary to multiple sclerosis is an extremely rare condition. When Gasserian ganglion block is performed, it is necessary to achieve reliable long-term analgesic effects while avoiding treatment-related complications.
Case Presentation: A 49-year-old male with multiple sclerosis exhibited persistent dull pain and paroxysmal electric shock-like pain in his bilateral maxillary molars and mandible.
Background: The goal of this study was to examine the effects of spinal cord stimulation (SCS) on muscle activity during walking after lower-limb amputation. Amputation results in a loss of sensory feedback and alterations in gait biomechanics, including co-contractions of antagonist muscles about the knee and ankle, and reduced pelvic obliquity range-of-motion and pelvic drop. SCS can restore sensation in the missing limb, but its effects on muscle activation and gait biomechanics have not been studied in people with lower-limb amputation.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!