Video coming soon — Dr. Luni explains cardiac arrest risk in plain language
What is sudden cardiac death?
Sudden cardiac death (SCD) is the unexpected stopping of the heart due to an abrupt loss of heart function. It is not the same as a heart attack, though a heart attack can trigger it. A heart attack is a plumbing problem — a blocked coronary artery. Sudden cardiac death is an electrical problem — the heart's electrical system suddenly fails, causing the heart to stop pumping blood effectively.
Without immediate treatment, sudden cardiac death is fatal within minutes. With prompt CPR and defibrillation, survival is possible — which is why public access to AEDs (automated external defibrillators) is so important.
What causes sudden cardiac death?
Sudden cardiac death can result from several different underlying problems. It is not caused by a single condition — rather, it is the final common pathway of various cardiac disorders. Common causes include:
- Ventricular fibrillation (VF): The most common arrhythmic cause of sudden cardiac death. The ventricles quiver chaotically instead of pumping — there is no effective heartbeat. VF is almost always fatal without immediate defibrillation.
- Ventricular tachycardia (VT): A rapid ventricular rhythm that can degenerate into VF if sustained. Fast, unstable VT can cause loss of consciousness and cardiac arrest.
- Coronary artery disease and heart attacks: The most common underlying structural cause. A heart attack can destabilize the heart's electrical system and trigger VF or VT.
- Cardiomyopathy: Weakening of the heart muscle — whether from prior heart attacks, viral infections, or genetic causes — creates an electrical substrate for dangerous arrhythmias.
- Hypertrophic cardiomyopathy (HCM): An abnormal thickening of the heart muscle, often genetic in origin, that can predispose to sudden cardiac death — particularly in young athletes.
- Arrhythmogenic cardiomyopathy (ARVC): A genetic condition in which heart muscle is replaced by fatty and fibrous tissue, creating a substrate for VT and VF.
- Genetic channelopathies: Inherited disorders of the heart's electrical channels — including Long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic VT (CPVT) — that can trigger life-threatening arrhythmias even in structurally normal hearts.
- Severe heart valve disease
- Commotio cordis: A rare cause in young athletes — a sudden blunt blow to the chest at a precise moment in the cardiac cycle that triggers VF.
Who is at high risk?
- Patients with prior heart attack and reduced heart function (low ejection fraction, particularly below 35%)
- Patients with hypertrophic cardiomyopathy (HCM)
- Patients with arrhythmogenic cardiomyopathy (ARVC)
- Patients with genetic channelopathies such as Long QT syndrome, Brugada syndrome, or CPVT
- Patients who have survived a prior cardiac arrest
- Patients with unexplained fainting (syncope), particularly during exercise
- Young athletes with an undiagnosed underlying heart condition
How is sudden cardiac death risk prevented?
ICD (Implantable Cardioverter Defibrillator)
An ICD is the most effective treatment for preventing sudden cardiac death in high-risk patients. The device continuously monitors the heart rhythm. If ventricular fibrillation or dangerous VT is detected, it delivers a precisely timed electrical shock within seconds — restoring normal rhythm automatically, without any action required by the patient.
Subcutaneous ICD (S-ICD)
For patients who do not need pacing, the S-ICD sits entirely under the skin with no leads inside the heart or blood vessels — reducing lead-related complications. Dr. Luni implants S-ICDs as part of his practice.
Catheter ablation
For patients with recurrent VT or VF, catheter ablation can eliminate or reduce the arrhythmia substrate — decreasing the number of dangerous episodes and ICD shocks. Ablation complements device therapy rather than replacing it in most high-risk patients.
Treating the underlying cause
Addressing the root cause — whether that is optimizing heart failure therapy, treating coronary artery disease, managing genetic conditions, or correcting reversible triggers such as electrolyte abnormalities or medication effects — is an essential part of reducing SCD risk.
If you have been told you are at risk for sudden cardiac death — or if you have a family history of unexplained sudden death, particularly at a young age — please seek evaluation by a cardiac electrophysiologist. This is a potentially life-saving conversation.