SCD continues to be the major mode of death of our population . Millions of men die every year instantly .The commonest mechanism is due to primary ventricular fibrillation following an abrupt closure of coronary artery due to a thrombus.Most die , within few minutes of the event, some before reaching the hospital , few within the ambulance and an unlucky few die on the CCU bed or cath lab table even after getting the best treatment.
If we analyse the data, there is a surprising fact ! Men form the bulk of these SCD victims.In our experience , out of 100 cases of consecutive in hospital primary VF only 6 were females , indicating an important biological phenomenon to be studied.The data for out of hospital primary VF is more difficult to get , but the log records of EMRI and emergency rescue team consistently confirm the male preponderance of primary VF .
How does the female heart enjoys this relative immunity from primary VF even as the blood supply is acutely compromised ?
The answer is not known . If we are able to decode this , one can replicate the same model in male .
The QT paradox and incidence of primary VF
QT interval represents a combination of electrical depolarisation and repolarisation .It is a well established scientific fact that women have relatively prolonged QT interval .This is determined by evolutionary biology and inherited characteristics of potassium channels during myocardial repolarisation
In simple terms, the female heart knows how to relax slowly and prolong the electrical relaxation time.(Not mechanical)
It is also a well known fact ischemia mediated a prolonged QT interval is a trigger for dangerous ventricular arrhythmia.This ischemia induced QT prolongation is less pronounced in females than males as the baseline QT itself is slightly longer in women.The percentage increment of QT interval during acute ischemia is significantly higher in male .This could be one reason for the preponderance of VF in men
The billion dolor question and a real challenge for the cardiologists is
How to make a heart electrically inert during ongoing ischemia ?
- Pain is also trigger for primary VF due to high adrenergic tone.Prompt control of chest pain make VF less likely.
- Lignoacaine a myocardial anesthetic if administered quickly can prevent many of the primary VF.
And now , shall we think little wildly !
What if , if we administer lignocaine spray straight over the (or sublingually ) in every patient with chest pain
as like a sport injury and try calm down the heart electrically !
1.Lignocaine the forgotten hero .