Abstract. Objective: To investigate out-of-hospital ventricular tachycardia (VT) cardiac arrest patients, comparing the prevalences and outcomes of the following VT subtypes among this population: monomorphic VT (MVT), polymorphic VT (PVT), and torsades de pointes (TdP, PVT with a prolonged QT interval). Methods: This was a retrospective review from a fire department-based paramedic system of nontraumatic VT cardiac arrest patients (January 1991 to December 1994) with a supraventricular perfusing rhythm (SVPR) at some time during out-ofhospital care, with a measurable QT interval. QT interval was measured from an SVPR, and corrected QT interval (QTc) was calculated and considered prolonged if > 0.45 sec. VT was classified as polymorphic or monomorphic. TdP was defined as PVT with a prolonged QT interval. Results: 196 patients were identified; six were excluded due to incomplete medical records, leaving 190 who met inclusion criteria and were used for data analysis. 117 (62%) patients had MVT, while 73 (38%) patients had PVT; of the 73 patients with PVT, 37 (51%) had normal QTc (non-TdP PVT) and 36 (49%) had prolonged QTc (TdP PVT). 97 (51%) patients had prolonged QTc (PQTc). Regardless of VT type (i.e., MVT vs PVT), 97 (51%) patients had prolonged QTc, with a mean QTc of 0.476 Ϯ 0.15 seconds prearrest and 0.464 Ϯ 12 seconds postarrest. Patients with PQTc were not more likely to have PVT (70 [37%] vs 76 [40%]; p = 0.705). No significant difference with respect to paramedic-witnessed arrests in each VT morphology group and each QT group was found. The overall hospital discharge rate was 28.4%. Regardless of VT type, patients had similar rates of out-of-hospital return of spontaneous circulation (ROSC) and hospital discharge; patients with PQTc were less likely to be discharged from the hospital (19.6% vs 37.6%; p = 0.01). 27.8% of TdP and 26.8% of non-TdP patients were discharged (p = 0.912). Conclusions: In this population of out-of-hospital VT arrest patients, MVT is the most common form of VT encountered; PVT and the subtype TdP are also seen in this population with approximately equal frequencies. All three rhythm types demonstrate similar responses to standard Advanced Cardiac Life Support therapy with equal rates of out-of-hospital ROSC and hospital discharge. PQTc may be a marker of poor clinical outcome in patients with out-of-hospital VT arrest. Key words: ventricular tachycardia; QT interval; polymorphic ventricular tachycardia; torsades de pointes; out-of-hospital; cardiac arrest. ACADEMIC EMERGENCY MEDICINE 1999; 6:609-617 S UDDEN cardiac death (SCD) represents a significant public health problem in the United States; ventricular tachycardia (VT) and ventricular fibrillation (VF) are frequently the car- 1,2 In many cases, VF is often preceded by VT; when classified from a morphologic perspective, VT is described as either monomorphic or polymorphic.2,3 Monomorphic VT (MVT) is frequently seen, easily diagnosed, and most often treated according to well-established guidelines in the out-of-hospital set...

Objective:To determine the prevalence and outcome of outof-hospital ventricular tachycardia (VT) cardiac arrest with a prolonged QT interval and to identify the subset with torsades de pointes (TdP). Methods: Design: Retrospective review. Setting: Fire departmentbased paramedic system. Participants: Non-traumatic VT cardiac arrest (1/91-12/94) with a supraventricular perfusing rhythm (SVPR) and a measurable QT interval. Interventions: QT interval was measured from a SVPR and corrected QT interval (QTc) was calculated (prolonged if >0.45 sec). VT was classified as polymorphic or monomorphic. Results: 190 patients met inclusion criteria. 51% of patients had a prolonged QTc (PQTc). The overall hospital discharge rate was 28.4%. No difference with respect to paramedic-witnessed arrests in each QTc group was found (25.8% normal QTc [NQTc] vs. 27.8% PQTc; p = 0.752). Patients with PQTc were less likely to be discharged from the hospital (19.6% vs. 37.6%; p = 0.01). Patients with PQTc were not more likely to have PVT (37% vs. 40%; p = 0.705). 16 (8.4%) patients had TdP. 27.8% of TdP and 26.8% of non-TdP patients were discharged (p = 0.912). Conclusions:Among this subset of patients with VT cardiac arrest, a majority have a PQTc and are less likely to survive compared to patients with NQTc. TdP is uncommon in this population and does not appear to affect survival.