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Palpitations are the perceived abnormality of the heartbeat characterized by awareness of cardiac muscle contractions in the chest: hard, fast and/or irregular beats. It is both a symptom reported by the patient and a medical diagnosis. Palpitation can be associated with anxiety and does not necessarily indicate a structural or functional abnormality of the heart, but it can be a symptom arising from an objectively rapid or irregular heartbeat. Palpitation can be intermittent and of variable frequency and duration, or continuous. Associated symptoms include dizziness, shortness of breath, sweating, headaches, and chest pain.
Palpitation may be associated with coronary heart disease, hyperthyroidism, diseases affecting cardiac muscle such as hypertrophic cardiomyopathy, diseases causing low blood oxygen such as asthma and emphysema; previous chest surgery; kidney disease; low levels of brain serotonin; blood loss, and pain; drugs such as antidepressants, statins, alcohol, nicotine, caffeine, cocaine, and amphetamines; electrolyte imbalances of magnesium, potassium and calcium; and deficiencies of nutrients such as taurine, arginine, and iron.
Signs and symptoms
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Three common descriptions of palpitation are "flip-flopping" (or "stop and start"), often caused by premature contraction of the atrium or ventricle, with the perceived "stop" from the pause following the contraction, and the "start" from the subsequent forceful contraction; rapid "fluttering in the chest," with regular "fluttering" suggesting supraventricular or ventricular arrhythmias (including sinus tachycardia) and irregular "fluttering" suggesting atrial fibrillation, atrial flutter, or tachycardia with variable block; and "pounding in the neck" or neck pulsations, often due to "cannon" A waves in the jugular venous pulsations that occur when the right atrium contracts against a closed tricuspid valve.
Palpitation associated with chest pain suggests coronary artery disease, or if the chest pain is relieved by leaning forward, pericardial disease is suspected. Palpitation associated with light-headedness, fainting or near fainting suggest low blood pressure and may signify a life-threatening abnormal heart rhythm. Palpitation that occurs regularly with exertion suggests a rate-dependent bypass tract or hypertrophic cardiomyopathy. If a benign cause for these concerning symptoms cannot be found at the initial visit, then ambulatory monitoring or prolonged heart monitoring in the hospital might be warranted. Noncardiac symptoms should also be elicited since the palpitations may be caused by a normal heart responding to a metabolic or inflammatory condition. Weight loss suggests hyperthyroidism. Palpitation can be precipitated by vomiting or diarrhea that leads to electrolyte disorders and hypovolemia. Hyperventilation, hand tingling, and nervousness are common when anxiety or panic disorder is the cause of the palpitations.
Palpitation can be attributed to one of four main causes:
- Extra-cardiac stimulation of the sympathetic nervous system (inappropriate stimulation of the sympathetic nervous system, particularly the vagus nerve (which innervates the heart), can be caused by anxiety and stress due to acute or chronic elevations in glucocorticoids and catecholamines. Gastrointestinal distress such as bloating or indigestion, along with muscular imbalances and poor posture, can also irritate the vagus nerve causing palpitations)
- Sympathetic overdrive (panic disorders, low blood sugar, hypoxia, antihistamines (i.e. levocetirizine), low red blood cell count, heart failure, mitral valve prolapse).
- Hyperdynamic circulation (valvular incompetence, thyrotoxicosis, hypercapnia, high body temperature, low red blood cell count, pregnancy).
- Abnormal heart rhythms (ectopic beat, premature atrial contraction, junctional escape beat, premature ventricular contraction, atrial fibrillation, supraventricular tachycardia, ventricular tachycardia, ventricular fibrillation, heart block).
Anxiety and stress
Anxiety and stress elevate the body's level of cortisol and adrenaline, which in turn can interfere with the normal functioning of the parasympathetic nervous system resulting in overstimulation of the vagus nerve. Vagus nerve induced palpitation is felt as a thud, a hollow fluttery sensation, or a skipped beat, depending on at what point during the heart's normal rhythm the vagus nerve fires. In many cases, the anxiety and panic of experiencing palpitations causes a sufferer to experience further anxiety and increased vagus nerve stimulation. The link between anxiety and palpitation may also explain why many panic attacks involve an impending sense of cardiac arrest. Similarly, physical and mental stress may contribute to the occurrence of palpitation, possibly due to the depletion of certain micronutrients involved in maintaining healthy psychological and physiological function. Gastrointestinal bloating, indigestion and hiccups have also been associated with overstimulation of the vagus nerve causing palpitations, due to branches of the vagus nerve innervating the GI tract, diaphragm, and lungs.
The most important initial clue to the diagnosis is one's description of palpitation. The approximate age of the person when first noticed and the circumstances under which they occur are important, as is information about caffeine intake (tea or coffee drinking), and whether continual palpitations can be stopped by deep breathing or changing body positions. It is also very helpful to know how they start and stop (abruptly or not), whether or not they are regular, and approximately how fast the pulse rate is during an attack. If the person has discovered a way of stopping the palpitations, that is also helpful information.
The diagnosis is usually not made by a routine medical examination and electrical tracing of the heart's activity (ECG), because most people cannot arrange to have their symptoms be present while visiting the doctor. Nevertheless, findings such as a heart murmur or an abnormality of the ECG, which could point to the probable diagnosis, may be discovered. In particular, ECG changes that can be associated with specific disturbances of the heart rhythm may be picked up; so routine physical examination and ECG remain important in the assessment of palpitation.
Blood tests, particularly tests of thyroid gland function are also important baseline investigations (an overactive thyroid gland is a potential cause for palpitations; the treatment in that case is to treat the thyroid gland over-activity).
The next level of diagnostic testing is usually 24 hour (or longer) ECG monitoring, using a recorder called a Holter monitor, which can record the ECG continuously during a 24-hour or 48-hour period. If symptoms occur during monitoring it is a simple matter to examine the ECG recording and see what the cardiac rhythm was at the time. For this type of monitoring to be helpful, the symptoms must be occurring at least once a day. If they are less frequent, the chances of detecting anything with continuous 24, or even 48-hour monitoring, are substantially lowered. More recent technology such as the Zio Patch allows continuous recording for up to 14 days; the patient indicates when symptoms occur by pushing a button on the device and keeps a log of the events.
Other forms of monitoring are available, and these can be useful when symptoms are infrequent. A continuous-loop event recorder monitors the ECG continuously, but only saves the data when the wearer activates it. Once activated, it will save the ECG data for a period of time before the activation and for a period of time afterwards - the cardiologist who is investigating the palpitations can program the length of these periods. An implantable loop recorder may be helpful in people with very infrequent, but disabling symptoms. This recorder is implanted under the skin on the front of the chest, like a pacemaker. It can be programmed and the data examined using an external device that communicates with it by means of a radio signal.
Investigation of heart structure can also be important. The heart in most people with palpitation is completely normal in its physical structure, but occasionally abnormalities such as valve problems may be present. Usually, but not always, the cardiologist will be able to detect a murmur in such cases, and an ultrasound scan of the heart (echocardiogram) will often be performed to document the heart's structure. This is a painless test performed using sound waves and is virtually identical to the scanning done in pregnancy to look at the fetus.
Treating palpitation will depend on the severity and cause of the condition. Palpitation that is caused by heart muscle defects will require specialist examination and assessment. Palpitation that is caused by vagus nerve stimulation rarely involve physical defects of the heart. Such palpitations are extra-cardiac in nature, that is, palpitation originating from outside the heart itself. Accordingly, vagus nerve induced palpitation is not evidence of an unhealthy heart muscle.
Treatment of vagus nerve induced palpitation will need to address the cause of irritation to the vagus nerve or the parasympathetic nervous system generally. It is of significance that anxiety and stress are strongly associated with increased frequency and severity of vagus nerve induced palpitation. Anxiety and stress reduction techniques such as meditation and massage may prove extremely beneficial to reduce or eliminate symptoms temporarily. Supplementation with certain nutrients such as taurine, citrulline (or arginine), GABA, and magnesium may also provide some reduction in nervous tension and anxiety,[unreliable medical source?] which in turn can help reduce symptoms. Changing body position (e.g. sitting upright rather than lying down) may also help reduce symptoms due to the vagus nerve's innervation of several structures within the body such as the GI tract, diaphragm and lungs.
With respect to the hyperstimulation of the vagus nerve, anticholinergic agents such as antihistamines or tricyclic antidepressants may inhibit the effect of acetylcholine in activating the vagus nerve thereby reducing its interference on the heart's normal rhythm.
- The Edge Effect, by Eric R. Braverman, M.D., 2004, pp. 142
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