Asystole: Causes, Risk Factors, and Clinical Prognosis

Cardiac arrest that results from the total failure of the cardiac electrical system is called asystole or flat-lining. 1 Asystole is a medical emergency that requires immediate recognition and intervention. This article will review the causes of asystole and the methods for diagnosing and treating patients with this condition.

Asystole Causes

Any condition that causes sudden cardiac arrest (SCA) or severe disruption of the cardiac electrical system can lead to asystole. 1 These causes must be considered immediately when asystole is identified in a patient to facilitate potential asystole reversal. 2

Reversible and Treatable Causes

Patients with SCA caused by any of the following are treatable 2:

  • Cardiac tamponade;
  • Coronary or pulmonary thrombosis;
  • Hypovolemia secondary to hemorrhage, dehydration, or infection 1,3;
  • Hypoxemia/hypoxia;
  • Hypokalemia;
  • Hyperkalemia (the most common electrolyte disorder associated with cardiac arrest);
  • Hypothermia;
  • Tension pneumothorax; and
  • Toxins.

Irreversible Causes and Progression

However, irreversible asystole causes include the following 3:

  • Weak or damaged cardiac muscle tissue, commonly due to coronary artery disease and cardiomyopathy 4;
  • Genetic conditions, like long QT syndrome; and
  • Inflammatory diseases, like sarcoidosis.

Any of these conditions can lead directly to asystole. More frequently, however, asystole develops in a patient after ventricular fibrillation, the most prevalent life-threatening arrhythmia. 1,4-5 Although many patients with these conditions will not experience SCA, they have more susceptibility to asystole and other forms of SCA.

Risk Factors

The risk profile for patients with SCA is similar to those with heart disease; therefore, patients with the following other risk factors are more susceptible 6:

  • Family history of coronary artery disease and/or myocardial infarction;
  • Family history of heart failure, arrhythmias, and genetic heart conditions;
  • Cigarette smoking;
  • Hypertension;
  • Hypercholesterolemia;
  • High body fat percentage;
  • Diabetes;
  • Sedentary lifestyle;
  • Personal or family history of sudden cardiac arrest;
  • Older age;
  • Male sex;
  • Substance use, including cocaine and amphetamines;
  • Obstructive sleep apnea; and
  • Chronic kidney disease.

Asystole Survival Rate & Prognosis

The prognosis for asystole is poor. In general, cardiac arrest survival rates are low, and the survival rate for patients whose initial rhythm is asystole is lower than for other forms of SCA. 7 According to the Cardiac Arrest Registry to Enhance Survival (CARES) 2022 annual report, the survival statistics are as follows:

  • 14.5% of patients with asystole survived to hospital admission.
  • 2.3% survived to hospital discharge.
  • 10.8% of hospitalized patients for whom the first documented rhythm is asystole survive to hospital discharge. 9

Complications and Brain Injury

For patients who survive cardiac arrest, complications are common and include neurologic dysfunction, brain injury, consciousness disorders, quality of life changes, neurocognitive deficits, and psychological effects. 10 Hypoxic-ischemic brain injury is the most prevalent neurological complication following cardiac arrest. This occurs because of cerebral reperfusion and the interaction of oxygen with reactive metabolites produced during ischemia. 10

The longer the period of ischemia, the greater potential for reperfusion injury. The injury may be worsened by brain edema and vasoconstriction occurring in response to reperfusion. Neuronal damage and death is the end result.