Sinus arrest, a term used interchangeably with sinoatrial arrest, is a disorder that involves failure of the sinoatrial node to discharge an electrical impulse for 2 seconds or more. It is associated with conditions such as sinus node dysfunction, certain drugs, myocardial infarction, and electrolyte imbalances (hyperkalemia). It may or may not be symptomatic.
Sinus arrest primarily affects older patients [1]. It may arise either as a manifestation of sinus node dysfunction, as a side effect from certain drugs used to treat cardiovascular diseases (eg. digitalis), as a complication of myocardial ischemia or sleep apnea, and alongside a fibrotic sinoatrial node condition [2] [3].
Depending on whether the arrest lasts for 2 seconds or for a longer period of time, sinus arrest causes symptoms ranging from mild/unnoticed to severe and life-threatening. Patients diagnosed with the condition usually belong to the senior age group and exhibit various comorbidities. The most common manifestations associated with sinus arrest include syncope, light-headedness, loss of orientation, weakness, angina, and heart failure [4] [5] [6]. Loss of consciousness experienced by a patient due to sinus arrest is known as Adam-Stokes attack. Oliguria may also complicate the clinical picture.
Sinus arrest during periictal period has been observed by a study to frequently arise in patients with inadequately controlled epilepsy [7]. In a typical sinus arrest case, should the electrical activity be paused for too long, different cellular groups will undertake the pacemaking responsibility until the sinoatrial node recovers. If that does not happen, sinus arrest can lead to hypoxia, multiple organ system failure, and cardiac arrest.
Sinus arrest is detected via a 12-lead electrocardiogram. Senior individuals who present with symptoms possibly originating from the cardiovascular system, such as angina, loss of consciousness, and fatigue, should always undergo an electrocardiographic evaluation.
A typical sinus arrest electrocardiogram (ECG) will reveal an absence of P waves, with a duration ≥ 2 seconds. Of note, the length of the pause cannot be expressed as a multiple of the basic sinus cycle length. Occasionally and when the P waves are absent for a relatively long time, escape beats appear, as other groups of myocardial cells undertake the pacemaking process for a brief period of time. The R-R interval before and after sinus arrest is stable.
Given that sinus arrest occurs as a result of sinus node dysfunction, myocardial ischemia, certain drugs, and other causes, these need to be investigated as well. Laboratory tests can illustrate a potential hyperkalemia, the ECG will also diagnose ongoing ischemic alterations of the myocardium, and ambulatory or long-term ECG monitoring can also be employed in order to investigate the presence of an underlying pathology and confirm where the symptoms originate from [8].