Dr.S.Venkatesan MD

When  a life leaves the body  silently in CCU , an  undulating  flat line in the monitor has a hidden scientific tale  to tell !

 

A  56 year old obese women died a instant death immediately after engaging the Left main ostium  after first injection of 5cc dye. The monitor showed only  a short pause, few sinus beats , a long pause , asystole and death . In the last 2 minutes of survival she threw a random wave forms of suggesting EMD . At any point of time she never showed any evidence for ventricular fibrillation . 1o minutes of intense resuscitation failed that included temporary pacing , repeated shocks  and ventilation.(ECMO /LV assist excluded)

What is the mechanism of death ?

• Is it electrical or mechanical ?
• Acute mechanical stunning / the stone heart ?
• Is it a primary electrical asystole ? (Acute sinus arrest or AV block )

Post hoc analysis of CAG did not show any significant clues except a tight distal left main.Apparently the catheter has triggered the event .( Or is it the  dye ? as some body suggested it as anaphylaxis  ?)

Even though we conveyed the message to the relatives,  it’s was an unexpected massive heart attack , obviously we were not convinced with our  uttering  ! Mind you , she had  normal LV function but had recurrent angina prior.

Image courtesy modified from http://www.ijaweb.org 2012 for representation purpose only.

We know if cardiac arrest is due to VF, it tends to give us  at-least some time and sense. Further,the VF protocols are more clear and success rate is more .

There is always an issue of  fine VF vs  asystole.If the flat line is indeed VF , there is more chance of revival as we try to pump adrenaline to make the fine VF  into coarse one  and shock again .The sequence can continue few times.

It is well known  asystole has a  dismal outcome .Even among the asystole there is some hope* if asystole is purely   electrical . (Like Stokes Adams in CHB or electrolytic asystole like hyperkalemia etc ) .But if asystole is due  mechanical cause , death ensues in spite of prompt temporary pacing .

* Important note : We have this  common  form of  treatable  mechanical asystole .It is called cardiac tamponade .It always present  with extreme bardycardia and asystole. It is extremely  rare to see a tamponade to present with VF. A prompt needle tap will do the job .It is vital  to recognise this in cath lab as our efforts are rewarding .

I would recommend a hand held echo machine , to hang like a catheter in every cath lab , ready to screen unexplained cardiac arrests with zero delay !

Why some hearts respond with VF  , while others go for asystole  with acute coronary insult ?

• A million Rupee question ! We are yet to find a legible answer .What is probable is  the the heart doesn’t  even have energy to fibrillate !
• The underlying disease need to be so intense .In this case it was left main stenosis supplying a truncated LAD and LCX. We could also see it supplying twigs to RCA  suggesting it to be a total occlusion .
• So ,when a  “physiologically single” coronary artery that precariously  supply the entire heart is suddenly insulted the heart behaves violently with runs of VT/VF. Our ignorance is complete when we realise  the heart  can do the opposite as well .It does not react at all , goes for a deep slumber and result in electro-mechanical sudden death.
• It is expected , in acute mechanical  deaths one may encounter flash pulmonary edema if the LV alone gets stunned. However , if both right and Left ventricle come to standstill in a synchronised sudden fashion , lungs will be as silent as deep sea . We believe this is what happened in our patient and it can be logically correlated  as  the critically narrowed left main was supporting the  RCA  as well.

Final message

Sudden cardiac deaths  9 out of 10 times is electrical . Majority  of them is  due to fibrillation. Next comes the electrical asystole ,Rarely (is that really rare ?) an ultra fast  sudden death due to mechanical asystole (Non -Tamponade ) is  possible , as experienced in our patient .

These mechanical asystole  are yet to be decoded.Whether it is a form  of Acute stunning , electro -mechanical uncoupling or mechano electrical standstill is not clear.