Palpitations are an unpleasant awareness of a forceful, rapid or irregular heart beat and are a source of panic, which could in turn worsen the condition. They are often harmless, but in some cases, may even be due to a life-threatening condition. Due to this, patients are often subjected to unnecessary tests. A detailed description of the symptoms by the patient can provide clues to the diagnosis of the cause of palpitations.
It is necessary to understand how the heart beats in order to comprehend the causes of palpitations. The heart acts as a pump with 2 upper chambers called the atria and 2 lower chambers called the ventricles. The heart receives blood into the atria when the atria are relaxed. The atria then contract and pump blood into the ventricles. This is followed by contraction of the ventricles. This contraction and relaxation cycle of the atria and ventricles is controlled by the electrical system of the heart, which consists of the sinoatrial node (SA node), the atrioventricular node (AV node) and electrical bundles and fibers. Impulses are generated in the SA node which acts as the pacemaker and travel through the atria; this results in atrial contraction. The impulses then reach the AV node, from where they spread to the ventricular muscles resulting in contraction of the ventricles.
An abnormality in rate and/or rhythm of heart beat is referred to as arrhythmia. Arrhythmias can often lead to palpitations.
Though the heart beats on its own, the rate and rhythm can be affected by inputs from nerves, chemical substances like adrenaline in the blood, and electrolyte and hormonal abnormalities.
Some of the sensations that a person feels during a palpitation are:
► Flip-flopping or ‘start and stop’ palpitations – These palpitations are a consequence of premature or early contractions of the atria and ventricles
► Fluttering of the chest – A regular fluttering in the chest suggests supraventricular or ventricular arrhythmia (an arrhythmia arising in the ventricle or just above the ventricle), whereas an irregular fluttering of the chest may indicate atrial flutter or fibrillation (abnormally fast and irregular contractions of the atria).
► Pounding in the neck – This type of palpitation is observed when the right atrium contracts against a closed heart valve.
The cause of palpitation may be diagnosed based on the type of palpitation and associated symptoms. Some of the associated symptoms that may help to clinch the diagnosis are:
► Palpitations associated with chest pain may be due to angina or heart attack.
► Palpitations with chest pain that is relieved when the patient moves forward may be due to pericardial disease (the pericardium is the tissue covering the heart).
► Palpitations associated with weight loss may be due to hyperthyroidism
► Palpitations following excessive vomiting or diarrhea may be due to dehydration and electrolyte abnormalities
► Palpitations due to anxiety or panic disorder are associated with hyperventilation, hand tingling and nervousness.
Tests used to diagnose the cause of palpitations include blood tests, 12-lead ECG and ambulatory monitoring devices. Blood tests include tests to check hemoglobin levels, electrolyte levels, kidney function tests and thyroid function tests. A 12-lead ECG can help to detect the cause of the palpitation. Ambulatory methods like the Holter monitor and the event recorder can be attached to the patient to record the heart’s activity over a particular period and study any abnormalities in the heart’s rate and rhythm.
The causes of palpitations are listed below:
Cardiac arrhythmias: Cardiac arrhythmias are abnormalities in the rate and / or rhythm of heart beats, which manifest as palpitations. An arrhythmia should be suspected in a patient with a known heart problem with palpitations occurring during sleep. The palpitations may be associated with lightheadedness and fainting episodes
Some cardiac arrhythmias that can result in palpitations are sinus bradycardia (where the heart rate is slower than normal), supraventricular and ventricular tachycardia (where the heart beats faster than normal), atrial fibrillation (where the upper chamber of the heart beats faster than normal), extrasystoles (where there are isolated extra beats) and heart block (where the impulses are not transmitted through the heart).
Cardiac arrhythmias are diagnosed with the help of an electrocardiogram. In some cases, continuous monitoring is needed throughout the day to detect the arrhythmia.
An arrhythmia leading to palpitation may be due to a cardiac and extra-cardiac cause. These causes include:
► Structural cardiac abnormalities: Structural abnormalities of the heart can cause palpitations due to alterations in blood flow through the heart chambers. These abnormalities include defects in the heart valves or in the septa (the partitions between the heart chambers). They may be present since birth or may appear later in life.
► Cardiac ischemia: Decreased blood supply to the heart muscles due to a block in the coronary arteries can precipitate an arrhythmia and result in palpitations. The patient has chest pain associated with the palpitations.
► Pericarditis: Inflammation of the pericardium or the covering of the heart is called pericarditis. Palpitation is accompanied by chest pain, which is relieved by bending forward.
Non-cardiac causes: Palpitations may be caused by factors outside the heart, which influence the heart rate and rhythm. These factors include:
► High output states: High output states are conditions where the heart has to beat faster. These conditions result in an alteration in heart rate and sometimes rhythm leading to palpitations. They include anemia, beriberi (deficiency of vitamin B1) and arterio-venous fistula. Excess thyroid hormone levels can cause the heart to beat faster and result in palpitations. The patient may have additional tremors, loss of hair and weight loss. Fever also increases the metabolic rate of the body and consequently the heart rate and results in palpitations.
► Hormonal changes: Hormonal changes during pregnancy can result in palpitations. Besides, palpitations may be more common before, during and after menopause.
► Dehydration: Dehydration due to conditions like prolonged vomiting or diarrhea cause abnormalities in electrolyte levels like potassium, magnesium, and calcium in the blood. These can affect the heart resulting in palpitations.
► Drugs: Prescription as well as over-the-counter medications can cause palpitations. These include pseudoephedrine, nitrates, overdose of digoxin or insulin, and asthma medications like albuterol inhalers or theophylline. Ephedra containing herbal medications and supplements can also cause palpitations and are banned by the US FDA. Thus, it is necessary to enquire into the medication history of a person who complains of palpitations. Illicit drugs like cocaine and marijuana can also cause palpitations. Their use may be considered in a person complaining of palpitations.
► Tea, coffee, tobacco and alcohol: Excessive intake of tea, coffee or alcohol, or cigarette smoking can cause symptoms of palpitations.
► Pheochromocytoma: Pheochromocytoma is a tumor of the adrenal gland, which secretes adrenaline. Excessive adrenaline in the blood makes the heart beat faster and results in arrhythmias.
► Hypoglycemia: Hypoglycemia or low blood sugar levels result in a faster heart beat. Thus, hypoglycemia should be ruled out in a patient complaining of palpitations especially if the patient is a diabetic.
► Physiological causes: Physiological conditions like exercise, stress, emotional and sexual excitement can cause palpitation. These are usually temporary and subside when the person is relaxed.
► Psychological / Psychiatric causes: Anxiety and panic disorders can lead to palpitations. Panic disorders are brief periods of overwhelming panic or terror that last for seconds or minutes and are accompanied by palpitations, shortness of breath and dizziness. The patient may give a history of previous panic attack. Palpitations in these conditions are a result in an increased release of substances like adrenaline in the body.
Frequently Asked Questions (FAQs)1. Which doctor should I visit in case I suffer from palpitations?
You should visit a cardiologist in case you suffer from palpitations.
2. Why is a continuous monitoring of the heart rate necessary in some cases?
In some cases, a continuous monitoring of the heart rate is necessary to detect changes in the heart rate and/or rhythm that may not be detected in the doctor’s office. For example, if a person has an abnormal heart beat at a particular time of the day or only associated with a particular activity, a Holter monitor, which detects cardiac activity throughout the day, will be able to pick up this abnormality.
Reference:1. Current Medical Diagnosis and Treatment 2012
2. PJ Mehta’s Practical Medicine 19th edition
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