Introduction: Phrenic nerve stimulation is a major obstacle in cardiac resynchronization therapy (CRT). Activation characteristics of the heart and phrenic nerve are different with higher chronaxie for the heart. Therefore, longer pulse durations could be beneficial in preventing phrenic nerve stimulation during CRT due to a decreased threshold for the heart compared with the phrenic nerve. We investigated if long pulse durations decreased left ventricular (LV) thresholds relatively to phrenic nerve thresholds in humans.
Methods And Results: Eleven patients, with indication for CRT and phrenic nerve stimulation at the intended pacing site, underwent determination of thresholds for the heart and phrenic nerve at different pulse durations (0.3-2.9 milliseconds). The resulting strength duration curves were analyzed by determining chronaxie and rheobase. Comparisons for those parameters were made between the heart and phrenic nerve, and between the models of Weiss and Lapicque as well. In 9 of 11 cases, the thresholds decreased faster for the LV than for the phrenic nerve with increasing pulse duration. In 3 cases, the thresholds changed from unfavorable for LV stimulation to more than a factor 2 in favor of the LV. The greatest change occurred for pulse durations up to 1.5 milliseconds. The chronaxie of the heart was significantly higher than the chronaxie of the phrenic nerve (0.47 milliseconds vs. 0.22 milliseconds [P = 0.029, Lapicque] and 0.79 milliseconds vs. 0.27 milliseconds [P = 0.033, Weiss]).
Conclusion: Long pulse durations lead to a decreased threshold of the heart relatively to the phrenic nerve and may prevent stimulation of the phrenic nerve in a clinical setting.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1111/jce.12345 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Dyspnea with Hemidiaphragm Elevation in a Patient with Giant Cell Arteritis: A Case Report.
Intern Med
January 2025
Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Japan.
We herein report the first case of dyspnea with hemidiaphragm elevation in a 68-year-old woman with active giant cell arteritis (GCA), including successful treatment. Contrast-enhanced computed tomography showed a reduced density of the left ophthalmic artery and the left superficial temporal artery with increased soft tissue compared to the other side, indicating that the GCA had flared up and suggesting that the hemidiaphragm elevation might be caused by vasculitis-associated ischemia of the right phrenic nerve. Hemidiaphragm paralysis due to vasculitis-associated ischemia in patients with GCA needs to be distinguished from local infection, tumors, and hepatomegaly, which are the major causes of hemidiaphragm elevation.
View Article and Find Full Text PDFThe Investing Layer of the Deep Cervical Fascia: An Alternative Site for Ultrasound-guided Supraclavicular Nerve Block - A Cadaveric Anatomical Study.
J Med Ultrasound
November 2024
Department of Anesthesiology, Ibra Hospital, Ibra, Oman.
Background: It is very well known that the supraclavicular nerve (SCN) which occupies the inferior part of the superficial cervical plexus basically originates from the ventral rami of C2-C4, then travels caudally into the investing layer of the deep cervical fascia (IL-DCF) alternatively termed the "prevertebral fascia."
Methods: This cadaveric study (a total of 6 soft-embalmed cadavers and bilateral dissections, i.e.
The Role of Gastrostomy and Noninvasive Ventilation in Primary Lateral Sclerosis.
Muscle Nerve
January 2025
Department of Neurosciences and Mental Health, ULS Hospital de Santa Maria, Lisbon, Portugal.
Introduction/aims: Literature on the role of gastrostomy and noninvasive ventilation (NIV) in primary lateral sclerosis (PLS) is limited. We aim to investigate whether PLS patients develop dysphagia requiring feeding tubes or respiratory failure necessitating NIV.
Methods: We conducted a retrospective study of PLS patients with a definite diagnosis followed at our center (1994-2024).
Optimized workflow with hybrid (very) high-power short-duration radiofrequency ablation renders point-by-point pulmonary vein isolation as fast and effective as cryoballoon ablation.
J Interv Card Electrophysiol
January 2025
Department of Cardiology, Thorax Center, Cardiovascular Institute, Erasmus MC, Rotterdam, the Netherlands.
Introduction: A hybrid approach with very high-power short-duration (vHPSD) posteriorly and ablation-index guided HPSD (50 W) anteriorly seems to be an optimal balance between efficiency and effectiveness for point-by-point pulmonary vein isolation (PVI). The aim of the current study is to compare vHPSD/HPSD ablation to cryoballoon ablation (CBA) in patients with symptomatic atrial fibrillation (AF).
Methods And Results: In this retrospective single-center study, we identified 110 consecutive patients who underwent their first PVI with either vHPSD/HPSD (n = 54) or CBA (n = 56).
Chloroquine Affects Presynaptic Membrane Retrieval in Diaphragm Neuromuscular Junctions of Old Mice.
Int J Mol Sci
December 2024
Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, MN 55905, USA.
Aging disrupts multiple homeostatic processes, including autophagy, a cellular process for the recycling and degradation of defective cytoplasmic structures. Acute treatment with the autophagy inhibitor chloroquine blunts the maximal forces generated by the diaphragm muscle, but the mechanisms underlying neuromuscular dysfunction in old age remain poorly understood. We hypothesized that chloroquine treatment increases the presynaptic retention of the styryl dye FM 4-64 following high-frequency nerve stimulation, consistent with the accumulation of unprocessed bulk endosomes.
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!