Complex arrhythmias are uncommon during pregnancy because of the relative young age and low prevalence of cardiac disease among pregnant women. In the near future, the increase in maternal age and concomitant medical diseases, such as obesity, chronic hypertension, diabetes with vasculopathy, and the fact that women are reaching childbearing age after surgical correction of congenital heart disease may increase the prevalence of arrhythmias during pregnancy.
The management of most arrhythmias during pregnancy is similar to standard practice applied to nonpregnant individuals. This chapter addresses the diagnosis and management of the most common arrhythmias found in clinical practice.
In most cases, heart rates above 150 beats per minute (bpm) are required for hemodynamic instability to occur. The mechanism by which the tachycardia leads to instability is related to the fact that at high heart rates, the ventricular filling time (time required to fill the left and right ventricles with blood) will be shorter than normal resulting in a reduction in stroke volume.
When caring for a patient with a tachyarrhythmia, the first step is to determine whether the patient is stable. If the patient has signs and symptoms of hemodynamic instability (eg, hypotension, angina, pulmonary edema, and confusion), then immediate synchronized electrical cardioversion is indicated. In stable patients, the pharmacological treatment is commonly indicated depending on the mechanism of the arrhythmia.
The first step in classifying the event is to divide them into either narrow or wide QRS (a wide QRS complex measures more than 0.12 seconds). Narrow QRS tachycardias may be either regular or irregular (depending on the distance between R waves on consecutive QRS complexes). Wide QRS tachyarrhythmias may be further subdivided into regular and irregular.
When caring for patients with new-onset arrhythmias, the clinician should look for potentially reversible causes, such as electrolyte abnormalities (as a general rule, maintain a potassium above 4 mEq/L and magnesium above 2 mg/dL), pH disturbances, as both alkalemia and acidemia may exacerbate arrhythmias, and, in cases of arrhythmias after central line placement, immediate assessment by chest X-ray is required to rule out the possibility that the tip of the catheter is inside the right atrium or right ventricle as its presence may precipitate arrhythmias. Thyroid evaluation with a thyroid-stimulating hormone level may also be indicated depending on the clinical presentation. Structural heart abnormalities need to be ruled out with a transthoracic echocardiography.
Narrow QRS-Regular Tachycardias
This first group includes the following: sinus tachycardia, atrial flutter with consistent atrioventricular conduction, atrioventricular nodal re-entrant tachycardia, atrioventricular reciprocating re-entrant tachycardia, and atrial tachycardia.1
The clinician should first rule out the possibility of a simple sinus tachycardia as this is commonly secondary to treatable conditions, such as pain, anxiety, hypovolemia, and fever. In general, sinus tachycardia has a gradual onset, and each QRS is preceded by ...