Sinus tachycardia is a common condition, in which the sinus rhythm exceeds 100 beats per minute. This results from an increase in the number of impulses arising from the sinus node. The prognosis of the condition is not too good, particularly in patients with cardiovascular diseases.
Patients with postural orthostatic sinus tachycardia may have additional symptoms including tremor, constipation, and bladder-related problems. They may find it difficult to tolerate extreme heat and cold, be intolerant to exercise, and have chronic fatigue. Tachycardia without any signs of underlying condition may indicate IST. On physical examination, significant findings are related to cardiovascular and respiratory systems. Patients are distressed. Some may present with chest discomfort due to tachycardia. The sinus rhythm will be higher than 100 beats per minute and may go up to 200 beats per minute in young individuals. In older individuals this value may be 150 beats per minute or less.
Electrocardiography (ECG) is the confirmatory diagnostic test for the different forms of sinus tachycardia. Differentiation between the different types like sinus node re-entry tachycardia and IST are important for deciding on the treatment regimen. ECG also helps to add more information regarding the cardiovascular cause of the condition. IST is characterized by heart rate of 100 beats per minute or more, followed by P-wave axis and morphology similar to that during sinus rhythm. In IST, the heart rate tends to become normal during sleep. Those with postural orthostatic sinus tachycardia show symptoms during upright posture. These patients may show an increase of <30 beats from baseline when in upright posture, but may not have a significant change in blood pressure during head upright tilt test.
Those with normal sinus tachycardia due to physical or mental exertion may not need any specific treatment. For other forms of sinus tachycardia, identifying and controlling the underlying cause is the main aim of any form of treatment. Non-pharmacologic strategies like increasing fluid consumption, high salt diet, and keeping the head at an elevated position during sleep help to expand plasma volume. Compression stockings with an ankle pressure of 30 mmHg is also recommended.
Beta blockers are the most common medications used in the management of symptomatic forms of normal sinus tachycardia, particularly those related to emotional stress or related to anxiety. They are also suggested for tachycardia with underlying congestive cardiac failure. But initial dosage and dosing intervals are carefully planned and monitored to avoid decompensation. Beta blockers are useful in IST as well. In case of postural orthostatic form of sinus tachycardia, beta blockers are combined with fludrocortisone. But this is generally done only after the failure of non-pharmacologic measures. Calcium channel blockers are also used in the management of symptomatic sinus tachycardia. This is useful in patients who are intolerant to beta blockers. It is effective in patients with sinus tachycardia secondary to acute myocardial infarction, and also in patients with IST. Alpha receptor agonists, central sympatholytic agents, and barbiturates are used for the management of postural orthostatic form of tachycardia.
Invasive therapy is generally not used in the treatment of normal and postural orthostatic sinus tachycardia. Catheter modification is occasionally used in the management of refractory forms of IST. This removes the cephalic region of the sinus node, but may lead to bradycardia and also the need for permanent pacing. Catheter modification is a useful strategy in the management of sinus node re-entry tachycardia, particularly in those patients who do not respond to drug therapy and those who have frequent episodes of tachycardia.
Prognosis of the different types of sinus tachycardia may depend on the underlying disease, if any. Those with normal sinus tachycardia have a good prognosis. Many studies have shown that high resting heartrate as an indicator of adverse prognosis. And this particularly true of patients with cardiovascular disease. Progressive increase in heartrate is associated with increased risk of cardiovascular and coronary mortality.
Sinus tachycardia is often a physiologic response to stresses including fever, anxiety, pain, hypoxia, hyperthyroidism, and hypovolemia . Stimulants like nicotine and caffeine, and certain medications like salbutamol and atropine, are also implicated as etiological factors in normal sinus tachycardia. Drugs like cocaine, amphetamines, and ecstasy can also cause sinus tachycardia.
In IST the baseline sinus rate may be elevated even in the absence of a physiologic stressor. Adults with IST may show elevated rate of resting heart beat, and minimal exercise may bring in an exaggerated response. Thus, IST is considered to be caused by hypersensitivity to autonomic stimuli or due to sinus node abnormality . Some other causes of sinus tachycardia include congestive heart failure, pulmonary embolism, acute myocardial infarction, cardiogenic shock, and inflammation.
Normal sinus tachycardia is the most common among sinus tachycardia. Symptomatic physiologic normal sinus tachycardia is more prevalent among females, while the other forms, including pathologic and pharmacologic, are present equally among males and females. IST is more common among females, and the average age of onset is about 30 years . Postural orthostatic sinus tachycardia is also reported to be more prevalent among females . There is no age or gender preference in sinus node re-entry tachycardia. Other epidemiological characteristics of the condition are lacking.
Rate of impulses from the sinus node is regulated by the autonomic tone, temperature, availability of oxygen, blood pH, and other hormonal factors. Sinoatrial nodal cells have an unstable membrane potential, and generate an impulse once every second . Most of the pharmacological and pathological etiological factors of sinus tachycardia result in faster depolarization of pacemaker by stimulating the beta adrenergic receptors which results in a faster heartbeat. Physiological causes of increase in heartbeat is driven by catecholamines.
In IST, the sinus nodal cells show enhanced automaticity . Excess of sympathetic with reduced parasympathetic tone also lead to IST. Abnormality in the baroreceptor reflex to orthostatic stress results in postural orthostatic sinus tachycardia. Even in the presence of a peripheral vascular resistance, and exaggerated tachycardia response is often lodged during orthostatic stress in this condition . Orthostatic tachycardia may also be caused by an exaggerated sympathetic response to physiological stimuli. Intrinsic sinus node abnormalities may also affect the normal sinus rhythm . In many other forms the pathophysiologic mechanisms are not clear. Patients who have orthostatic intolerance often show reduced venous compliance, particularly in the legs. This may lead to the specific symptoms .
The best way to prevent sinus tachycardia is to reduce the risk of cardiovascular disease. Those who have an underlying heart disease should monitor it carefully and treat the condition. Avoiding causes like alcohol, caffeine, and nicotine also goes a long way in preventing the development of sinus tachycardia.
Sinus tachycardia is a common sinus rhythm, in which the rhythm exceeds 100 beats per minute in adults. This results from an increase in the number of impulses arising from the sinus node. The prognosis of the condition is not too good, particularly in patients with cardiovascular diseases . Although very common, sinus tachycardia is often overlooked. Normal heart beat rate in adult ranges from 60 to 100 beats per minute, while in infants it may be 110-150 beats per minute. The increased rate gradually slows down in children as they grow older. Sinus tachycardia may be classified into four distinct forms of rhythm disturbances:
Sinus tachycardia is a condition in which the heart rate is elevated, usually above 100 beats per minute. This rate is higher than the normal resting heart rate of an individual, which ranges from 60-100 beats per minute. It may go up to 200 beats per minute in younger individuals, while it may be around 150 beats in older people. Increase in heart rate is usually a response to physiological conditions like exercise, anger, and emotional stress. Some other causes of sinus tachycardia include pain, fever, inflammation, anxiety, dehydration, heart failure, hyperthyroidism, lack of oxygen, and chronic pulmonary disease. Thus sinus tachycardia generally reflects an underlying condition or an effect of certain medication. Many forms of sinus tachycardia is found to be more common among females when compared to males.
Sinus tachycardia may remain asymptomatic, but many may present with features like dizziness, lightheadedness, and palpitations. Patients who have underlying heart disease may not be able to tolerate sinus tachycardia. Tremor, constipation, and bladder-related problems are also noted as symptoms in some patients. Prognosis of this condition depends on the severity of underlying condition. In general, sinus tachycardia has a good prognosis. But, progressive increase in heart rate is associated with many heart diseases.
Electrocardiography (ECG) is the most important tool in the diagnosis of this condition along with the clinical symptoms. Identifying the underlying cause of the disease is very important in deciding on appropriate treatment strategy. If the condition is caused by certain medications, slow tapering of the medication is suggested. Some of the common medications used in the treatment include beta blockers and calcium channel blockers. Invasive procedures like catheter modification is used only in cases of refractory sinus tachycardia. Sinus tachycardia is treated without any specific medication as well. Those with normal sinus tachycardia due to physical or mental exertion may not need a specific treatment. Non pharmacologic strategies like increased fluid consumption, having a high salt diet, and keeping the head at an elevated position during sleeping helps to relieve the symptoms. Compression stockings with an ankle pressure of 30 mmHg is also recommended. Reducing the risk of heart diseases is the best way to prevent the development of this condition. Those who have any form of heart disease or metabolic diseases should monitor and treat the condition. Avoiding the use of causative factors like nicotine, alcohol and caffeine is also important.