Definition
Absence of ventricular complexes on the ECG or absence of ventricular activity (electrical–mechanical dissociation).
ECG Features
- Ventricular asystole can result from severe sinoatrial block or arrest or by third-degree AV block without a junctional or ventricular escape rhythm; ECG features include:
- P waves present if patient has complete AV block (Figure 1)
- P waves absent during asystole if patient has severe sinoatrial block or arrest
- No QRS complexes
- Electrical–mechanical dissociation-a recorded ECG cardiac rhythm (P-QRS-T) and no effective cardiac output or palpable femoral pulse.
Pathophysiology
Ventricular asystole represents cardiac arrest; if the ventricular rhythm is not restored in 3–4 minutes, irreversible brain injury can occur.
Systems Affected
- Cardiovascular
- All organ systems affected by loss of perfusion
Genetics
N/A
Incidence/Prevalence
Unknown
Geographic Distribution
None
Signalment
Species
Dog and cat
Breed Predilections
None
Mean Age and Range
Unknown
Signs
Historical Findings
- Severe systemic illness or cardiac disease in many patients
- Other cardiac arrhythmias in some
- Syncope
Physical Examination Findings
- No ventricular pulse can be palpated
- Cardiac arrest
- Collapse
- Death
Causes
- Complete AV block with absence of ventricular or junctional escape rhythm.
- Severe sinus arrest or block.
- Hyperkalemia (Figure 2).
Risk Factors
- Any severe systemic illness (e.g., severe acidosis and hyperkalemia) or heart disease.
- Hypoadrenocorticism causing hyperkalemia.
- Urinary tract rupture or obstruction, resulting in hyperkalemia.
