Understanding and preventing sudden cardiac death

Every two minutes, an American life is lost to sudden cardiac death (SCD). As the name suggests, SCD can strike without warning, and is often the result of an abrupt change in the heart’s electrical rhythm. While a heart attack (myocardial infarction) can lead to sudden cardiac death, these terms are not interchangeable. People can (and frequently do) survive heart attacks, whereas sudden cardiac death represents the loss of life due to a cardiac cause, within one hour of symptom onset.

Although heart attacks and other cardiovascular conditions remain major health concerns, SCD is particularly notable for its abrupt and unpredictable occurrence. Heart attacks are frequently the result of atherosclerotic cardiovascular disease (ASCVD), which takes decades to develop. This is why we see heart attacks almost entirely in older adults. Sudden cardiac death, on the other hand, can strike even the youngest and healthiest among us. In fact, you’ve probably heard at least one story of a young athlete collapsing during a game. These are often cases of sudden cardiac arrest (SCA), which can quickly progress to SCD if not reversed.

There are many potential causes of sudden cardiac death, but they fit into a few groups. These are well-summarized in Figure 1, from an article in the New England Journal of Medicine. You’ll see that the majority (around 80%) are the result of ASCVD, the decades-long process that affects older individuals disproportionately. In this bucket, there will be warning signs and opportunities for prevention if someone is receiving adequate medical care.

Figure 1: A breakdown of the causes of sudden cardiac death (Huikuri et al., 2001).

The remaining 20% are causes that can affect anyone, at any age. These include structural heart abnormalities, which can develop as a result of infections, drugs, autoimmune conditions, and more. They can also simply be the result of genetics, and this is often the case when a young athlete experiences SCD. These are things we can see, typically with an echocardiogram (heart ultrasound), but it’s not common practice to have this performed for screening purposes. Many people go decades without experiencing any symptoms from a structural heart abnormality, and unfortunately SCD can be the first thing to occur. 

There are some rare causes of SCD we can’t see, which include genetic issues with the heart’s electrical conduction system. Though these are more difficult to diagnose and treat, they can be managed if caught in time on an EKG (electrocardiogram).

For all causes of SCD, prevention comes down to two aspects: screening to avoid sudden cardiac arrest in the first place, and immediate treatment to stop SCA from becoming SCD. Screening for SCD risk is not very robust currently, though this remains up for debate. Thus far, the general thought is that strategies like rhythm monitoring or echocardiography (heart imaging) are not accurate enough and are too costly on the population level.

While this could change in the future, for now we’re largely left with trying to manage SCA when it occurs. This is why it’s so critical to get CPR-certified, and add yourself to the 18% of Americans already certified in Basic Life Support (BLS). CPR and early defibrillation with an automated external defibrillator (AED) are the mainstays of survival, and with just a few hours of training, anyone can be prepared to save a life.

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