Respiratory sinus arrhythmia
| Respiratory sinus arrhythmia | |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Ogheneochuko Ajari, MB.BS, MS [3]
Synonyms and keywords: RSA
Overview
Respiratory sinus arrhythmia (RSA) refers to the normal slowing down of heart rate during expiration (breathing out) and speeding up of heart rate during inspiration. Heart rate is normally controlled by centers in the medulla oblongata. One of these centers, the nucleus ambiguus, increases parasympathetic nervous system input to the heart via the vagus nerve. The vagus nerve decreases heart rate by decreasing the rate of SA node firing. Upon expiration, the cells in the nucleus ambiguus are activated and heart rate is slowed down. In contrast, inspiration triggers inhibitory signals to the nucleus accumbens and consequently the vagus nerve remains unstimulated.[1]
Causes
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
Common Causes
- Normal variation in vagal tone
Causes by Organ System
| Cardiovascular | Atherosclerosis, congestive heart failure, hypertension, hypercapnia, myocardial infarction, normal variation in vagal tone |
| Chemical/Poisoning | No underlying causes |
| Dental | No underlying causes |
| Dermatologic | No underlying causes |
| Drug Side Effect | Anidulafungin, digitalis, guanfacine, morphine |
| Ear Nose Throat | No underlying causes |
| Endocrine | No underlying causes |
| Environmental | No underlying causes |
| Gastroenterologic | No underlying causes |
| Genetic | No underlying causes |
| Hematologic | No underlying causes |
| Iatrogenic | No underlying causes |
| Infectious Disease | No underlying causes |
| Musculoskeletal/Orthopedic | No underlying causes |
| Neurologic | No underlying causes |
| Nutritional/Metabolic | Hypercapnia, obesity |
| Obstetric/Gynecologic | No underlying causes |
| Oncologic | No underlying causes |
| Ophthalmologic | No underlying causes |
| Overdose/Toxicity | Digitalis |
| Psychiatric | No underlying causes |
| Pulmonary | No underlying causes |
| Renal/Electrolyte | Hypercapnia |
| Rheumatology/Immunology/Allergy | No underlying causes |
| Sexual | No underlying causes |
| Trauma | No underlying causes |
| Urologic | No underlying causes |
| Miscellaneous | No underlying causes |
Causes in Alphabetical Order
- Anidulafungin
- Atherosclerosis
- Congestive heart failure
- Digitalis
- Guanfacine
- Hypertension
- Hypercapnia
- Morphine
- Myocardial infarction
- Normal variation in vagal tone
- Obesity
Diagnosis
Electrocardiogram
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EKG of a patient with acute inferior myocardial infarction shows sinus bradycardia (59 bpm) and respiratory sinus arrhythmia (please note to rhythm line at the bottom). QRS=104 msec, PR=172 msec
On an electrocardiogram (EKG), RSA is seen as subtle changes in the R-R interval (time between two of the distinctive, large, upward "R" spikes on an electrocardiogram) synchronized with respiration. The R-R interval on an EKG is shortened during inspiration and prolonged during expiration. Meditation and relaxed breathing techniques can temporarily alter RSA.
References
- ↑ Neff RA, Wang J, Baxi S, Evans C, Mendelowitz D (2003). "Respiratory sinus arrhythmia: endogenous activation of nicotinic receptors mediates respiratory modulation of brainstem cardioinhibitory parasympathetic neurons". Circ Res. 93 (6): 565–72. doi:10.1161/01.RES.0000090361.45027.5B. PMID 12907666.