One-fourth of patients use drugs that cause arrhythmia; Their doctors are unaware

23% of patients prescribed drugs are using at least one that causes arrhythmias. More than 80% of healthcare professionals agree that EKGs should be given before and after prescribing such drugs. But less than 1% of healthcare professionals can name a single drug that causes arrhythmia.

STRAFFORD [drugINTEL - 14 Feb 2003 - According to a report in the American Journal of Medicine, 23% of patients receive prescriptions for drugs that prolong QT Interval, and one tenth of these receive more than one drug affecting QT interval, according to a recently released study. "QT Interval" refers to the time during which the heart gathers its energy for its next contraction - the "backswing" of the heart, as it were. Disturbing this part of the heart's cycle can cause Arrhythmias (also described as Torsades de Pointes or palpitations) that can be lethal. It was this effect of Propulsid (cisapride) that led to a $100 million verdict in Mississippi in 2001.

Half of the drugs known to prolong QT interval prescribed in this study were antidepressants, e.g. Prozac (fluoxetine) and Zoloft (sertraline). Antibiotics were often common, e.g., Clarithromycin, Levofloxacin, and Erythromycin.

The lay journals point out that physicians may be aware of the risks but decide that nonetheless the benefits justify the use of the drugs. Another explanation might be that deaths caused by increasing QT Interval are relatively rare, despite the crystal clear causation, so that physicians are prepared to ignore the theory in favor of practice. However, studies (see below) show that less than 1% of healthcare professionals including physicians are able to name any drugs that prolong QT interval.

81% of these same healthcare specialists in cardiology who were surveyed agreed that for safety's sake, QT interval should be measured after the patient starts using the drug to determine its impact on the individual. FDA has tightened restrictions greatly during the last decade against permitting drugs onto the market if they increase QT interval, to the consternation of the pharmaceutical research sector, now obliged to discard as much as half their promising new drugs because of this common side effect. FDA was forced to recognize that either pharmaceutical companies were educating insufficiently or doctors were not learning fast enough about the QT issues to keep these drugs on the market. If withdrawing Propulsid was meant to send a message to the pharmaceutical industry, it appears to not have made much impact.

How about the other side of the story? Of course, some drugs have a bigger effect on QT interval and almost every medical research scientist will agree that these are risky. (Clearly, not every physician will agree - probably less than 1% of them can agree.) The Sudden Arrhythmia Death Syndromes (SADS) Foundation specializes in drugs and conditions causing QT interval prolongation, and points to a more conservative set of lists of drugs that prolong QT interval. Their short list of drugs comprises 23 drugs (not including Propulsid (cisapride), which was withdrawn from the market because of this effect.)

Conclusion: Based on the figures in the American Journal of Medicine article, patients who suffer Heart Attacks have about a one in four chance of having used one drug and a 2% chance of using multiple drugs that can cause Arrhythmias and hence Cardiac Arrest, and (based on Al-Khatib et al. 2003) a 100-to-1 chance that the physician was oblivious to the risk and therefore Failed to Inform the patient.

Lesley H. Curtis, Truls Ostbye, Veronica Sendersky, et al.

Prescription of QT-prolonging drugs in a cohort of about 5 million outpatients

American Journal of Medicine 1 February 2003, Volume 114, Issue 2 Pages 135-141

Al-Khatib SM, LaPointe NM, Curtis LH, Kramer JM, Swann J, Honig P, Califf RM.

Outpatient prescribing of antiarrhythmic drugs from 1995 to 2000.

Am J Cardiol. 2003 Jan 1;91(1):91-4.