Study Looks to Predict Sudden Cardiac Arrest Risk

A promising new way to predict sudden cardiac arrest risk has been identified by medical researchers at the University of Buffalo.

For patients who are at the highest risk of sudden cardiac arrest, this is exciting news, as this research may give cardiologists an advanced screening tool to help those in the high-risk category and those most likely to benefit from receiving an implantable cardiac defibrillator (ICD).

ICDs are mainly used to prevent sudden cardiac arrest in patients with advanced heart disease, but many patients’ devices are never triggered.

New research suggests that imaging the degradation of nerve function in the heart may identify those patients at greatest risk of developing a life-threatening heart rhythm.

Using Positron Emission Tomography (PET), in the largest PET imaging study ever done on sudden cardiac arrest, researchers were able to measure the amount of nerve damage within the muscular tissue of the heart.

PET imaging is also able to show where nerves have died or become damaged due to inadequate blood flow.

Sudden cardiac arrest

“The principal question we posed with this study was whether the amount of nerve damage in the heart could predict sudden cardiac arrest,” says James A. Fallavollita, author on the study. “We found that when at least 38 percent of the heart was showed signs of nerve damage, there was a significant increase in the risk of sudden cardiac arrest.”

At this time, to determine whether an ICD is needed, doctors take a measurement of heart function called the ejection fraction; the percentage of blood pumped by the heart with each beat. An ejection fraction of 35 percent or less is a strong indicator of sudden cardiac arrest risk; these patients usually require an ICD.

This research is a prime example of translational medicine (the emerging field which focuses on using what is learned in pre-clinical studies to do smarter things in the clinic). In this case, the pre-clinical studies demonstrated that the risk of developing ventricular fibrillation (a deadly heart rhythm) was related to regional nerve damage.

“Ultimately, we wanted to develop an approach that could tackle the problem of identifying a larger portion of the patients with coronary artery disease who are at risk of developing sudden cardiac arrest,” explains John M. Canty, a principal investigator of the research. “Since many patients who suffer a cardiac arrest do not have severely depressed heart function, PET imaging may be able to identify high risk individuals who, in the future, could be considered candidates for an ICD.”

Cardiac Re-synchronization Therapy

As part of our mission here at Iridia to promote heart disease, we are constantly drawing awareness to Automated External Defibrillators (AEDs) and their importance in fighting Sudden Cardiac Arrest (SCA). One area we haven’t talked is  the “what comes next area.” What happens when you survive a SCA or are diagnosed with heart disease? There are treatment options available and Cardiac Resynchronization Therapy (CRT) is one of them.

Cardiac Re-synchronization Therapy

CRT is used to treat the delay in heart ventricle contractions that occur in some people with advanced heart failure.

In other words, CRT is a therapy to provide a weakened heart with the ability to be re-synced and restore proper pumping functions.

Currently, CRT is one of the most advanced cardiac treatment options available for heart disease sufferers.

In order to re-sync the heart, a CRT pacing device (also called a biventricular pacemaker) is surgically implanted under the skin. This specially designed pacemaker stimulates the lower chambers of the heart to contract at the same time, making the heart more effective and efficient.

How does a Biventricular Pacemaker work? When a heart rate drops below a set rate (programmed by a doctor), the pacing device generates small electrical impulses that pass through the leads to the heart muscle. Theseimpulses make the lower chambers of the heart muscle contract, causing the right and left ventricles to pump together. In many cases, the end result is improved cardiac function.

Cardiac Re-synchronization Therapy

Studies have shown CRT improves symptoms of heart failure in about 50% of patients. Many of these patients had previously been treated with medications but still suffered severe or moderately severe heart failure symptoms.

CRT not only improves survival, but also quality of life, heart function, ability to exercise, and helps decrease hospitalizations in many patients with severe heart disease.

The procedure itself is generally very safe. Given the success of CRT, if an individual is a good candidate for the procedure, CRT will give them an increased chance at a normal life.

Cleveland Clinic, a non-profit academic medical research centre, has shown that on average, CRT improves the amount of blood pumped out with each heart beat by 5% to 10%. In some cases, patients with a CRT device can even develop normal ventricular function. It is not rare for a patient to see an increase of blood pumped out by each beat by up to 40%.

Given the health benefits, it is unfortunate that CRT is not available to all heart disease sufferers. CRT is only appropriate for people who:

  • have severe or moderately severe heart failure symptoms
  • are taking medications to treat heart failure
  • have delayed electrical activation of the heart 
  • have a history of cardiac arrest or are at risk for cardiac arrest

What does the future hold for CRT? According to recent studies, allowing implantation of CRT devices in patients with moderate heart failure could help stem progression of heart failure.

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM) is a disease of the heart where the certain elements of the heart muscle is thickened. The thickening can lead to a misalignment of the muscle cells, which can lead to disruptions in the electrical functions of the heart.

Hypertrophic Cardiomyopathy

You might not have heard of HCM before, but you’ve likely heard of its effects in the news (Fabrice Muamba, Alexander Dale Oen) as HCM is a leading cause of sudden cardiac death in young athletes. 

Unfortunately, the younger the individual diagnosed with HCM is, the more likely they have a more severe form of hypertrophic cardiomyopathy.

The signs and symptoms of Hypertrophic Cardiomyopathy are usually very mild, but can include shortness of breath, chest pain, unusual heart palpitations, fatigue, fainting and sudden cardiac death.

Often, HCM shows no symptom before sudden cardiac death occurs, making HCM difficult to diagnose and treat. There are several risk factors that will increase the probability of sudden cardiac death:

  • HCM diagnosed at a young age (less than 30)
  • An episode of sudden cardiac arrest
  • Family history of HCM with sudden death
  • Recurrent fainting

However, knowing these factors, it is possible to be prepared for a sudden cardiac arrest. In patients who are deemed to be high risk, an implantable cardioverter defibrillator (ICD) may be implanted. An ICD is the most effective and reliable treatment option available. There are also surgical options involving open heart surgery for patients who remain severely symptomatic.

One other option for those with HCM is to have an Automated External Defibrillator (AED) on hand in the event a sudden cardiac arrest occurs. When an AED is applied within the first 3 minutes of cardiac arrest, the chances of survival can increase to 75 percent or more.

Recently, Iridia held a contest in honour of heart month,  to giveaway an AED to a person or organization in need. Aside from helping a person in need, the giveaway was meant to highlight the importance of AEDs and raise awareness of these life-saving devices.

Hypertrophic Cardiomyopathy - Free AED

The winner of our AED Giveaway, the Kopytko family, whose young child, Mitchell, was born with HCM are ecstatic that they no longer have to worry if there is an AED around or not.

“As a parent I spend much of my day worrying that if he were to have a cardiac incident it would be too late by the time it was recognized, and the paramedics were called,” said Melanie, his mother.

Read the Kopytko story

It is our belief that AEDs should be publically accessible. In recent years, AEDs have made great headway in this respect, but we still have a ways to go. You just never know who will be walking through a mall or an airport when an AED will be needed.  All we can do is be prepared.