Datapoints: Prevalence of QT Prolongation Among Veterans With Severe Mental Illness

The QT interval refers to the time required for the heart to repolarize after ventricular depolarization. The U.S. Food and Drug Administration (FDA) has issued Drug Safety Communications on drugs associated with QT prolongation and fatal ventricular arrhythmias. Antidepressants received attention after the 2011 FDA communication on citalopram, often prescribed off-label for posttraumatic stress disorder (PTSD).

Aggregated data (diagnosis codes and outpatient prescriptions) were examined for all Veterans Health Administration (VHA) patients treated between October 2005 and September 2009. Among 7.1 million patients, 1,224 had a diagnosis of QT prolongation (ICD−9 code 426.82). Chi square tests assessed the association of prior-year severe mental illness with QT prolongation.

Among patients with QT prolongation, the mean age was similar to that for all VHA patients (about 61 years). However, rates of severe mental illness were higher (28% versus 12% for all VHA patients). Risk factors for QT prolongation included gender (35 females versus 16 males per 100,000) and African-American race (31 per 100,000 versus 20 for all patients). QT prolongation among patients with severe mental illness was nearly triple that among patients without severe mental illness (40 per 100,000 versus 14), and it was elevated for specific illnesses (Figure 1). Citalopram was prescribed to 8% of the study sample, more commonly for patients with PTSD (16%) or major depression (21%). Receipt of any drug associated with QT prolongation varied by illness: without severe mental illness, 14%; schizophrenia, 20%; PTSD, 24%; and major depression, 28%.

Findings highlight the need to reevaluate types and combinations of medications that may potentiate heart disease or death among patients with severe mental illness. A study limitation is that the data precede the 2011–2012 FDA Drug Safety Communications, and citalopram use may change in the wake of the warnings.