Why am I asked to do regular ECGs on my medications?
ECG also known as Electrocardiogram. This in simple terms is a tracing of the heart.
The heart consists of 4 chambers (two upper known as the atrium and lower 2 known as ventricles).
The action of the heart depends on depolarization and repolarization of the cells.
Now don’t get bogged down by the technicalities but this just means the way a cell changes its charge due to movement of sodium ions in and out.
Anyway, ECG is a tracing of the heart which measures these functions and it indicates if the heart is functioning optimally.
ECG has 3 main components:
P wave which represents the depolarization of the atria
QRS complex which represents the depolarization of the ventricles
T wave, which represents the repolarization of the ventricles.
Now what is QT interval and why is this important to people consulting psychiatrists?
QT interval is the time interval from beginning of the QRS complex ( denotes ventricular depolarization) to end of the T wave ( denoting ventricular repolarization).
Normal QT interval is around 400 to 440 milliseconds ( in women QT interval is normally longer than men).
Now as a rule of thumb doctors look at the T wave in relation to the RR interval ( the time between 2 R waves). If this is somewhat in the middle, then QT interval is normal. If it shifts to the right then it is prolonged.
There are some formulas which even help doctors calculate the corrected QT interval ( one of them is Bazett’s Formula).
If the QT interval is prolonged more than the normal and above 500 milliseconds it is possible that the patient may suffer a form of ventricular arrhythmia known as Torsades de pointes which is a serious complication. Hence it is vital that the QT interval is kept within normal limits.
There are many drug and non-drug causes of QT interval prolongation.
There are some risk factors that predispose to prolonged QT interval. This includes being female, increasing age, pre-existing cardiac issues, hypertension, diabetes mellitus and high body mass index.
Some older anti psychotics, anti-depressants and some antibiotics, anti-malarial can cause prolonged QT interval.
Lurasidone, Paroxetine, Fluvoxamine, Sertraline Carbamazepine, Valproate, Lamotrigine, Benzodiazepines, Gabapentin
and Pregabalin are known to be the safer options.
Using lowest possible dose, avoiding too many polypharmacy and slow titration of dose and regular 6-12 monthly monitoring of ECG are all recommended if patients are on QT prolonging medications.
In Chennai Minds, the safety of our patients are paramount. Patients sometimes ask us why they require to take ECG.
One of the reason is to monitor the QT interval and I think this blog enumerates in detail explaining why you require ECG to monitor the QT interval.