Introduction:
QT prolongation is associated with increased risk of ventricular arrhythmias.As many patients with COVID19 may be started on QT prolonging drugs, measuring and monitoring QT is imperative to prevent fatal ventricular arrhythmias. However, we need to limit exposure of staff to patients with confirmed COVID19 and judiciously use personal protective equipment. Thus, it is important to find alternatives to doing frequent 12-lead ECGs.
Hypothesis:
We hypothesize that the QT interval measured from telemetry is similar to the QT interval on 12-lead ECG.
Methods:
Telemetry recordings and 12-lead ECGs were obtained from 15 patients at the same time and identical heart rates. Patients were from two different inpatient units with the same telemetry monitoring service. QT intervals were measured manually using calipers with the tangent method, excluding U waves. Telemetry recordings included lead I and II or a precordial lead. QT from telemetry was compared to the corresponding leads and to the longest QT on the 12-lead ECG. In cases of atrial fibrillation (AF), the QT from all the complexes was averaged.
Results:
Of 15 patients, 2 were in AF and 2 had RBBB. One patient had abnormal T-wave morphology and QT prolongation (abnormal repolarization). In all patients, QT intervals from the same leads as telemetry matched the QT measured from 12-lead. In 14 of 15 patients, telemetry QT matched the longest QT on the 12-lead ECG. However, in the patient with abnormal repolarization, maximum QT on 12-lead ECG was substantially longer than telemetry QT (Figure 1).
Conclusion:
When using the same lead, QT intervals were identical on telemetry and 12-lead ECG. However, in the patient with abnormal repolarization, the longest QT on 12-lead ECG was not represented on telemetry. In patients with abnormal repolarization on 12-lead ECG, we recommend serial 12-lead ECGs while on QT-prolonging drugs. Telemetry may suffice as a surrogate for 12-lead ECG to follow QT intervals in most patients.
Factorization in the multirefined tangent method
