Led by researchers from the University of Padua, together with various hospitals and the Agency for Environmental Prevention and Protection for the Veneto Region in Padua, Italy, the research looked at how air pollution affected the increase of ventricular arrhythmia occurrence in patients who have been implanted with cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy defibrillators (ICD-CRT).
Ventricular arrhythmia is a condition where abnormal heart rhythms come from the lower chambers of the heart (or ventricles). These rhythms, in turn, can cause the heart to beat too fast, preventing the delivery of oxygen-rich blood to the brain and other parts of the body – which may lead to a cardiac arrest. (Related: Many BPA-free bottles contain a chemical that causes arrhythmia, hyperactivity and brain changes.)
The condition has two common types:
- Ventricular fibrillation is when there is an "extremely rapid heart rhythm" in the lower heart chambers. These are noted to be at around 300 beats per minute (BPM) – when the normal resting heart rate is between 60 to 100 BPM. Death immediately follows a ventricular fibrillation unless resuscitation is applied.
- Ventricular tachycardia, on the other hand, is a rapid heart rhythm that clocks in anywhere between 150 to 250 BPM. Some medications may slow down the rhythm to 110 to 150 BPM. The condition may impede the heart's function of effectively pumping heart to the entire body, resulting in loss of blood flow to vital organs.
To prevent this from happening, implantable cardioverter-defibrillators (ICDs) are installed in patients with known ventricular arrhythmia. The ICD sends an electric shock to the heart once it detects an abnormal heart rhythm to stabilize it. Meanwhile, a cardiac resynchronization therapy (CRT) device shoots small electrical impulses to the ventricles to allow them to beat in a synchronized pattern, improving the blood pumping ability of the heart.
The researchers first looked at earlier studies to determine any existing link between air pollution and ventricular arrhythmia. While the results may be different, a common link that all studies pointed out is that patients with coronary heart diseases are more prone to the effects of air pollutants.
To understand the link, researchers utilized data from ARIA, a prospective multicenter study which collated data pertinent to atrial and ventricular arrhythmia – that is, an abnormal heart rhythm in the upper and lower chambers. This was then measured using a diagnostic device which transmitted data each time a relevant arrhythmic or technical event was detected in a patient. In total, data from 281 patients were culled across nine cardiologic centers in Veneto, Italy.
As for air quality data, particularly for particulate matter concentrations less than 10 micrometers (PM10) and 2.5 ?m (PM2.5), these were collected from monitoring stations daily. Aside from particulate matter, carbon monoxide, nitrogen dioxide, sulfur dioxide, and ozone were gathered as well. Each patient was grouped with the exposure data from the monitoring station closest to them.
The study ran from April 1, 2011 to Septemeber 30, 2012, with a follow-up conducted within a year after the review, and a closing visit was done a year after.
The researchers discovered that episodes of ventricular tachycardia and ventricular fibrillation were associated with PM2.5 but not PM10. They also found that incidences of ventricular fibrillation also increased when the levels of PM2.5 and PM10 were higher. Other gaseous pollutants, however, did not have a noticeable correlation with ventricular tachycardia or ventricular fibrillation. In particular, patients with a previous case of myocardial infarction had a pointed association with ventricular tachycardia or ventricular fibrillation as well.
The authors believe that the results of the study will bolster claims to consider environmental conditions when addressing arrhythmic events, especially in patients with coronary heart disease.
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