Sinus arrhythmia refers to an irregular sinus rhythm characterized by more than 10% variation in the P-P interval. Normal sinus rhythm may show slight variability in the different complexes in individuals.
Sinus arrhythmia, in most of the cases, remains asymptomatic and may not be clinically significant. An increase in peripheral pulse rate during inspiration is common in patients with this condition. The rate may decrease during expiration. Symptoms of non-respiratory sinus arrhythmia depends on the underlying condition that causes the abnormality in rhythm. It is often detected during slower heart rate. Some of the less common symptoms of the condition include:
Vertigo and syncope are noted in more severe forms of sinus arrhythmia.
Sinus arrhythmia is often detected while checking for some other unrelated condition or symptom. The three general diagnostic techniques used in sinus arrhythmia include medical history, physical examination and ECG. Medical history of the patient will help to find the presence cardiac diseases, if any. Medications are also taken into consideration. Previous experiences of rhythm abnormalities and their treatment is also important. Physical examination focuses on heart and peripheral vasculature. Pulse is palpated to check for rate and regularity.
An ECG is the confirmatory diagnostic test for sinus arrhythmia. To identify sinus arrhythmia, all complexes in the ECG are ensured to be identical. P-P interval of the two fastest complexes is calculated along with P-P interval for two slowest complexes. Difference between the two (two fastest and two shortest) P-P intervals is the confirmatory diagnostic measure for sinus arrhythmia. If the difference between the two is greater than 0.16s, it is considered to be sinus arrhythmia. Both P-P and R-R interval tend to be shorter during inspiration and longer during expiration . Heart rate usually remains within normal limits of 6o bpm to 100 bpm. In some cases, the rate may be less than 60 beats per minute. Heart rate also shows variation during the respiratory cycle, increasing during inspiration and decreasing during expiration . Configuration and size of P wave remain normal, but PR interval may vary slightly within the limits. QRS complex and T wave also have normal configuration. QT interval may vary, but within normal limits. As sinus arrhythmia has a slow rhythm, changes may be recorded only after a few seconds. Rhythm strip should be kept in original size so as to trace the abnormalities in rhythm. In most of the cases of respiratory sinus arrhythmia the rhythmical changes in heart rate are recurring and predictable . Flat ST complex changes, both in the form of depressions or elevations, may represent ischemic condition and need further evaluation.
Specific treatment for sinus arrhythmia is not recommended when it is asymptomatic. If the condition is a non-phasic variant, the underlying condition should be treated for relieving symptoms. Monitoring the heart rhythm is important to determine whether it is coinciding with the respiratory cycle of the patient. Rhythm should be carefully evaluated to avoid inaccurate interpretations of the condition. If sinus arrhythmia is caused by medication, it should be discontinued depending on the situation. Respiratory sinus arrhythmia is presumed to be beneficial in pulmonary gas exchange and also in improving the energy efficiency of pulmonary circulation . Propantheline 15 mg three times a day is recommended to reduce the amplitude of arrhythmia and to relieve the symptoms of respiratory sinus arrhythmia assessed at 20% . Long term treatment with anticholinergic agents is found to improve the condition in 75% of the patients .
Sinus arrhythmia, particularly the phasic variant, remains asymptomatic in most of the cases and may not require any specific treatment. Prognosis of non-respiratory variant of sinus arrhythmia depends on the underlying cause and the treatment initiated. In most of the cases, the condition is not associated with any specific precautions or restrictions as in many other cardiovascular conditions.
Normal variations in the vagal tone is the most common etiologic factor of sinus arrhythmia. It may also be produced by certain pathologic conditions including:
Under normal conditions, vagal tone may reduce during inspiration resulting in increased heart rate. The complexes in an ECG may thus fall together, shortening the P-P interval, a feature characteristic of sinus arrhythmia. An increase in vagal tone during expiration reduces the heart rate leading to lengthening of P-P interval.
Some types of arrhythmia are common but information on population prevalence of many of these are not available. Respiratory sinus arrhythmia is a normal phenomenon in children and athletes. Non-respiratory form of sinus arrhythmia is less common when compared to respiratory or phasic sinus arrhythmia. It has a pathological etiology and is typically found in elderly patients . Incidence of respiratory sinus arrhythmia is found to decrease with age. This is presumed to be related to decrease in carotid distensibility and baroreceptor sensitivity in old age.
During respiratory sinus arrhythmia, vagal tone reduces with increased blood flow back to heart. Reduction of vagal tone increases the heart rate shortening the P-P interval. At the time of expiration, venous return to the heart decreases, increasing the vagal tone. Heart rate slows down and P-P interval lengthens . These transient variations in the heart rate during the respiratory cycle are noted on an ECG or a rhythm strip. It is all the more evident if the normal rate is bradycardic. It is because of this reason, respiratory sinus arrhythmia is more commonly seen during lower heart rates and in athletes. Sinus arrhythmia is also common among young children and it gradually disappears as they get older . It may also disappear when the heart rate increases as in use of atropine or during exercise .
Non-phasic sinus arrhythmia is not associated with the normal respiratory cycle or physiology. The P-P interval may vary randomly without a gradual increase or decrease in the heart rate and often occurs spontaneously. A recent report show that some patients may have a change in the location of the main pace maker in the sinus node. This transient change may be triggered by vagal stimulation from one area to other. Change of stimulation to the lower pole of the sinoatrial node from upper pole changes the structure and interval of P waves. Abnormalities in impulse formation and conduction may also lead to arrhythmias including sinus arrhythmia.
Most of the cases of sinus arrhythmia are a normal variation in the P-P interval and cannot be prevented. Non-respiratory sinus arrhythmias are caused by underlying conditions and hence preventing the actual cause is the best way to avoid variations in the heart beat.
Sinus arrhythmia refers to an irregular sinus rhythm characterized by more than 10% variation in the P-P interval. Normal sinus rhythm may show slight variability in the different complexes in individuals. This variability is usually smaller than 0.16 seconds. But in some patients this irregularity may show interval variability of more than 0.16 seconds, which is categorized as sinus arrhythmia. This condition is often identified with gradual widening and narrowing of the P-P intervals. It can be measured by calculating the difference between the longest and shortest P-P intervals. This difference would be more than 0.16s in patients with sinus arrhythmia. Sinus arrhythmia is divided into two types:
Sinus arrhythmia is also found in association with complete heart block. This condition normally occur in children, athletes and older adults, but is very rarely seen in infants. Both phasic and non-phasic sinus arrhythmia may aggravate during deep breath.
Sinus arrhythmia refers to abnormal rhythm in heart beat. There are two types of sinus arrhythmia – respiratory and non-respiratory. Respiratory sinus arrhythmia is a normal variation in the heart beat, originating from the pace maker of the heart, the sinoatrial node. Respiratory form of sinus arrhythmia is usually found in children, athletes and older adults. Non-respiratory sinus arrhythmia is associated with certain pathological conditions. It may be produced by heart diseases, increased pressure in the cranium, myocardial infarction, use of certain medications like digoxin and morphine. Respiratory sinus arrhythmia improves with age in children when the heart beat increases.
This condition is caused by a change in the messaging by vagus nerve. During inspiration, there is an increase in the flow of blood to the heart which stimulates the vagus. This increases the heart beat and brings about a change in the ECG. During expiration, blood flow into the heart decreases which stimulates the vagus to slow down heart rate. Sinus arrhythmias may not produce any specific symptoms and may not be very significant. But a considerable variation in the ECG, particularly in elderly patients, may indicate other serious conditions and needs attention.
Patients with sinus arrhythmias may have increased pulse rate during inspiration which decreases during expiration. It is easily noted when the heart rate is lower. When the heart rate is higher, as in exercise, abnormality in the rhythm may disappear. If sinus arrhythmia is caused by underlying conditions or diseases, signs and symptoms specific to that may develop. Severe cases are marked by dizziness and fainting.
Treatment is generally not needed for this condition, unless symptoms are present. If it is a non-respiratory type of sinus arrhythmia, the underlying cause needs to be treated. Continuous monitoring of heart rhythm is very important to see whether the rhythm coincides with inspiration and expiration. Accurate checking of the ECG wave is also important in diagnosis of the condition. Medical history, physical examination and ECG are the diagnostic techniques used in the workup. Presence of a heart disease or condition has to be considered along with the type of medications taken. Since certain drugs are known to cause this condition, it is important to let the physician known about the use of the medication. ECG is the confirmatory test for both the types of sinus arrhythmia.
Prognosis of the condition depend on the underlying cause. Respiratory sinus arrhythmia is a normal variation in the heart beat and may not be significant. There are no known preventive measures for controlling sinus arrhythmia.