Palpitation

Etiology

The current knowledge of the neural pathways responsible for the perception of the heartbeat not clearly elucidated. It has been hypothesized that these pathways include different structures located both at the intracardiac and extracardiac level. Palpitations are a widely diffused complaint and particularly in subjects affected by structural heart disease. The list of etiologies of palpitations is long, and in some cases, the etiology is unable to be determined. In one study reporting the etiology of palpitations, 43% were found to be of cardiac etiology, 31% of psychiatric etiology and approximately 10% were classified as miscellaneous (medication induced, thyrotoxicosis, caffeine, cocaine, anemia, amphetamine, mastocytosis).[1] 

The cardiac etiologies of palpitations are the most life-threatening and include ventricular sources (premature ventricular contractions, ventricular tachycardia and ventricular fibrillation), atrial sources (atrial fibrillation, atrial flutter) high output states (anemia, AV fistula, Paget's disease or pregnancy), structural abnormalities (congenital heart disease cardiomegaly, aortic aneurysm, or acute left ventricular failure), and miscellaneous sources (postural orthostatic tachycardia syndrome POTS, Brugada syndrome, and sinus tachycardia).[1][2]

Palpitations can occur during times of catecholamine excess, such as during exercise or at times of stress.  The cause of the palpitations during these conditions is often a sustained supraventricular tachycardia or ventricular tachyarrhythmia.  Supraventricular tachycardias can also be induced at the termination of exercise when the withdrawal of catecholamines is coupled with a surge in the vagal tone.  Palpitations secondary to catecholamine excess may also occur during emotionally startling experiences, especially in patients with a long QT syndrome.[1][2]

Many psychiatric conditions can result in palpitations including depression, generalized anxiety disorder, panic attacks, and somatization. However one study noted that up to 67% of patients diagnosed with a mental health condition had an underlying arrythmia. [1][2][3]

There are many metabolic conditions that can result in palpitations including, hyperthyroidism, hypoglycemia, hypocalcemia, hyperkalemia, hypokalemia, hypermagnesemia, hypomagnesemia, and pheochromocytoma.[1][2]

The medications most likely to result in palpitations include; sympathomimetic agents, anticholinergic drugs, vasodilators and withdrawal from beta blockers.  Common etiologies also include excess caffeine, or marijuana.  Illicit drug use such as cocaine, amphetamines,  3-4 methylenedioxmethamphetamine (Ectasy or MDMA) and can also cause palpitations.[1][2][4]

Epidemiology

Palpitations are a very common complaint in the general population, and particularly in those affected by structural heart disease. Clinical presentation is divided into four groups: extrasystolic, tachycardic, anxiety-related, and intense. Anxiety-related is the most common. [5]

Pathophysiology

The sensation of palpitations can arise from extrasystoles or tachy-arrythmias. It is very rarely noted due to bradycardia. Palpitations can be described in many ways. The most common descriptions include a flip-flopping in the chest, a rapid fluttering in the chest, or pounding in the neck. The description of the symptoms may provide a clue regarding the etiology of the palpitations, and the pathophysiology of each of these descriptions is thought to be different.  In patients who describe the palpitations as a brief flip-flopping in the chest, the palpitations are thought to be caused by extra systoles such as supraventricular or ventricular premature contractions. The flip-flop sensation is thought to result from the forceful contraction following the pause and the sensation that the heart is stopped results from the pause. The sensation of rapid fluttering in the chest is thought to result from a sustained ventricular or supraventricular arrhythmia. Furthermore, the sudden cessation of this arrythmia can suggest paroxysmal supraventricular tachycardia.  This is further supported if the patient can stop the palpitations by using Valsalva maneuvers. The rhythm of the palpitations may indicate the etiology of the palpitations (irregularly irregular palpitations indicate atrial fibrillation as a source of the palpitations). An irregular pounding sensation in the neck can be caused by atrioventricular dissociation, and the subsequent atria are contracting against a closed tricuspid and mitral valves, thereby producing cannon A waves.  Palpitations induced by exercise could be suggestive of cardiomyopathy, ischemia or channelopathies.[2][6]  

History and Physical

A complete and detailed history and physical examination are two essential elements of the evaluation of a patient with palpitations. The key components of a detailed history include, age of onset, description of the symptoms including rhythm, situations that commonly result in the symptoms, mode of onset (rapid or gradual), duration of symptoms, factors that relieve symptoms (rest, Valsalva), positions and other associated symptoms such as chest pain, lightheadedness or syncope. A patient can tap out the rhythm to help demonstrate if they are not currently experiencing the symptoms. The patient should be questioned regarding all medications, including over the counter medications. Social history, including exercise habits, caffeine consumption, alcohol, and illicit drug use, should also be determined. Also, past medical history and family history may provide indications to the etiology of the palpitations.

Palpitations that have been a condition since childhood are most likely caused by a supraventricular tachycardia, whereas palpitations that first occur later in life are more likely to be secondary to structural heart disease. A rapid regular rhythm is more likely to be secondary to paroxysmal supraventricular tachycardia or ventricular tachycardia, and a rapid and irregular rhythm is more likely to be an indication of atrial fibrillation, atrial flutter, or tachycardia with variable block.  Supraventricular and ventricular tachycardia is thought to result in palpitations with an abrupt onset and abrupt termination.  In patients who can terminate their palpitations with a Valsalva maneuver, this is thought to indicate possibly a supraventricular tachycardia.  Palpitations associated with chest pain may suggest myocardial ischemia. Lastly, when lightheadedness or syncope accompanies the palpitations, ventricular tachycardia, supraventricular tachycardia, or other arrhythmias should be considered.

Unfortunately, patients are rarely experiencing palpitations when the health care provider examines them. A complete physical exam should be performed including vital signs (with orthostatic vital signs) cardiac auscultation, lung auscultation, and examination of extremities.  A patient can tap out the rhythm to help demonstrate what they felt previously if they are not currently experiencing the symptoms. 

Positive orthostatic vital signs may indicate dehydration or an electrolyte abnormality. A midsystolic click and murmur may indicate mitral valve prolapse.  A harsh holosystolic murmur best heard at the left sternal border which increases with Valsalva may indicate hypertrophic obstructive cardiomyopathy. Fixed splitting of the S2 throughout the cardiac cycle and a right ventricular heave are characteristic clinical features of the atrial septal defect. An irregular rhythm indicates atrial fibrillation or atrial flutter. Evidence of cardiomegaly and peripheral edema may indicate heart failure and ischemia or a valvular abnormality.[1][2][6]

Evaluation

A 12-lead electrocardiogram must be performed on every patient complaining of palpitations. The presence of a short PR interval and a delta wave (Wolff-Parkinson-White syndrome) is an indication of the existence of ventricular pre-excitation. Significant left ventricular hypertrophy with deep septal Q waves in I, L, and V4 through V6 may indicate hypertrophic obstructive cardiomyopathy. The presence of Q waves may indicate a prior myocardial infarction as the etiology of the palpitations, and a prolonged QT interval may indicate the presence of the long QT syndrome.

Laboratory studies should be limited initially.  Complete blood count can assess for anemia and infection. Serum urea, creatinine and electrolytes to assess for electrolyte imbalances and renal dysfunction. Thyroid function tests may demonstrate a hyperthyroid state. 

Most patients have benign conditions as the etiology for their palpitations. The goal of further evaluation is to identify those patients who are at high risk for an arrhythmia. Recommended laboratory studies include an investigation for anemia, hyperthyroidism and electrolyte abnormalities. Echocardiograms are indicated for patients in whom structural heart disease is a concern.

Further diagnostic testing is recommended for three groups of patients. Those in whom the initial diagnostic evaluation (history, physical examination, and EKG) suggest an arrhythmia, those who are at high risk for an arrhythmia, and those who remain anxious to have a specific explanation of their symptoms. Patients who are considered to be at high risk for an arrhythmia include those with organic heart disease or any myocardial abnormality that may lead to serious arrhythmias. These conditions include a scar from myocardial infarction, idiopathic dilated cardiomyopathy, clinically significant valvular regurgitant, or stenotic lesions and hypertrophic cardiomyopathies.

An aggressive diagnostic approach is recommended for those high-risk patients and can include ambulatory monitoring or electrophysiologic studies.  There are three types of ambulatory EKG monitoring devices: Holter monitor, continuous-loop event recorder, and an implantable loop recorder. The Holter monitor is a 24-hour monitoring system that is worn by the patient and records and continuously saves data. Holter monitors are worn for a few days. The continuous-loop event recorders are also worn by the patient and continuously record data, but the data is saved only when the patient manually activates the monitor. The continuous-loop recorders can be long worn for longer periods of time than the Holter monitors and therefore have been proven to be more cost-effective and efficacious than Holter monitors. Also, because the patient triggers the device when they feel the symptoms, they are more likely to record data during palpitations. An implantable loop recorder is a device that is placed subcutaneously and continuously monitors for cardiac arrhythmias. These are most often used in patients with unexplained syncope and can be used for longer periods of time than the continuous loop event recorders. An implantable loop recorder is a device that is placed subcutaneously and continuously monitors for the detection of cardiac arrhythmias. These are most often used in patients with unexplained syncope and are a used for longer periods of time than the continuous loop event recorders. Electrophysiology testing enables a detailed analysis of the underlying mechanism of the cardiac arrhythmia as well as the site of origin. EPS studies are usually indicated in patients with a high pretest likelihood of a serious arrhythmia.[1][2][6]

Treatment / Management

The management of palpitations is determined by the underlying cause of the symptoms. Radiofrequency ablation can cure most types of supraventricular and many types of ventricular tachycardias.[7] The most challenging cases involve palpitations that are secondary to supraventricular or premature ventricular contractions(PVCs) or associated with normal sinus rhythm. These conditions are thought to be benign, and the management involves reassurance of the patient that these arrhythmias are not life-threatening. However, symptomatic or frequent PVCs(>10,000 PVCs/24 hours EKG monitoring or >10% of all beats) require treatment. Up to 1/3rd of the patients with frequent PVCs develop PVC induced cardiomyopathy and progressive left ventricular dysfunction. First-line therapy for symptomatic or frequent PVCs is B-blocker or calcium channel blockers. Patients who are refractory to medical therapy or who develop left ventricular dysfunction should undergo catheter ablation of the PVCs. Catheter ablation leads to the resolution of PVC induced cardiomyopathy in most patients.[7](B3)

Patients who present to the emergency department who are asymptomatic, with unremarkable physical exams, have non-diagnostic EKGs and normal laboratory studies, can safely be sent home and instructed to follow up with their primary care provider or cardiologist. Patients whose palpitations are associated with syncope, uncontrolled arrhythmias, hemodynamic compromise, or angina should be admitted for further evaluation. PVCs are common and are usually benign.

Differential Diagnosis

• Arrhythmias

• Atrial fibrillation/flutter

• Bradycardia caused by advanced atriovenous block or sinus node dysfunction

• Bradycardia-tachycardia syndrome

• Multifocal atrial tachycardia

• Premature supraventricular or ventricular contractions

• Sinus tachycardia or arrhythmia

• Supraventricular tachycardia

• Ventricular tachycardia

• Wolff-Parkinson-white syndrome

Pertinent Studies and Ongoing Trials

While catheter ablation is currently a common treatment approach, there has been advances in stereotactic radioablation for certain arrythmias.  This technique is commonly used for solid tumors and has been applied with success in management of difficut to treat Ventricular Tachycardia and Atrial Fibrillation.[8]

Direct to consumer options for monitoring of heart rate and heart rate variability has become increasingly prevalant using smart phones and smart watches.  These monitoring systems have become increasingly validated and may help provide early identification for those at risk for a serious arrythmia such as atrial fibrillation.[9]