Identifying the underlying cause is essential for management of palpitations in pregnancy. Differential diagnoses for palpitations are as follows.
The physiological state of pregnancy is associated with significant haemodynamic changes associated with adaptation of the cardiovascular system to deal with the metabolic requirements of the mother and her growing fetus. Consequently, maternal heart rate increases by 25%; thus sinus tachycardia, particularly in the third trimester, is not uncommon. Premature atrial beats (‘ectopic beats’) and non-sustained arrhythmia are encountered in more than 50% of pregnant women.
Palpitations are unpleasant sensations of irregular and/or forceful beating of the heart. They can occur in women with no known heart disease or rhythm abnormalities. Palpitations, dizziness, pre-syncope and even syncope frequently occur during pregnancy. The reasons for these palpitations remain unknown. In others, palpitations result from abnormal heart rhythms (arrhythmias). Palpitations are most often caused by cardiac arrhythmias or anxiety. Cardiac arrhythmias can be identified on Holter recordings in up to 60% of normal people under the age of 40 years. It is therefore not uncommon to see women complaining of palpitations while pregnant.
Arrhythmias refer to heartbeats that could be slow, too fast, irregular or too early. Palpitations can result from many arrhythmias, including any bradycardia and tachycardia, premature ventricular and atrial contractions, sick sinus syndrome, advanced arterio-venous block or ventricular tachycardia. Episodes of ventricular tachycardia and supraventricular tachycardia may be perceived as palpitations but also can be asymptomatic or lead to syncope .
Rapid arrhythmias (greater than 100 beats/minute) are called tachycardias.
Slow arrhythmias (slower than 60 beats/minute) are called bradycardias.
Irregular heart rhythms are called fibrillations.
When a single heartbeat occurs earlier than normal, it is called a premature contraction, and this can cause the sensation of a forceful heartbeat.
Abnormalities in the atria, the ventricles and the electrical conducting system [the sino-atrial (SA) node and the atrio-ventricular (AV) node] of the heart can lead to arrhythmias that cause palpitations.
Non-arrhythmic cardiac problems, such as mitral valve prolapse, pericarditis and congestive heart failure, and non-cardiac problems, such as hyperthyroidism, vaso-vagal syncope and hypoglycaemia, can cause palpitations. Palpitations also can result from stimulant drugs, over the counter and prescription medications. No cause of palpitations can be found in up to 16% of patients.
A common sensation of palpitation in the absence of concomitant cardiac arrhythmias may also be related to physiological changes occurring during pregnancy, such as increased heart rate, decreased peripheral resistance and increased stroke volume.
A study looking at the incidence of arrhythmias in normal pregnancy and relation to palpitations, dizziness and syncope demonstrated a high incidence of arrhythmias, mostly ventricular ectopic activity, in young healthy women presenting with symptoms of palpitations, dizziness or syncope during their pregnancy .
Increased sympathetic activity during pregnancy has been proposed as a mechanism for increased incidence of arrhythmias.
Structural heart disease
Congenital heart disease creating reentry circuit
Acyanotic, for example, atrial septal defect/ventricular septal defect
Cyanotic, for example, tetralogy of Fallot
Valvular, for example, bicuspid aortic valve
Valvular disease secondary to rheumatic fever
Valvular disease secondary to endocarditis
Structurally normal heart
Congenital, for example dual AV nodal pathway/Wolff–Parkinson–White syndrome
Degenerative disease of the conduction system
Acquired long QT syndrome, for example drugs, metabolic
Metabolic – hyperthyroidism
Prescription drugs, for example digitalis, phenothiazine, β-agonists
Street drugs (e.g. cocaine)