Bradycardia is a common cardiac arhythmia. Sinus bradycardia is often considered an arrhythmia from a disciplined heart. It denotes high vagal tone . A heart rate of 40 , some times even 35 is well tolerated . But bradycardia due to heart blocks are dangerous.
Sinus bradycardia can not get lower than 30/mt or so , as invariably either the junction or the ventricle , escapes with its own rhythm. Near syncope, dizziness , giddiness followed by syncope occur as the heart rate slows progressively below this level .It is often taught humans can not survive when the heart rate goes below 10/mt .
Case report :
Here is middle-aged man who presented with a history of recurrent syncope over a period of 3 days . He has no history of CAD.
As he entered the ER, this ECG was recorded.
At this pint of time , when the ECG was recorded, he was conscious and talking , only to complain of little dizziness. After seeing this ECG , he was immediately put on a temporary pacemaker.
Note : The ECG shows a single qrs complex per tracing of 10 sec duration .Ie HR of 6 /mt.One qrs complex for 50 large squares ! .Divide 300/50 and HR is 6 . Note also the p waves fire at 150/mt due to atropine effect .
The procedure took 15 minutes to perform , he was comfortable and was administered atropine , and isoprenaline *, which increased his heart rate from 6/mt to 10/mt .
Later he went on to receive a permanent pacemaker a week later.
* Temporary trans-cutaneous pacing using paddle stickers is an another modality available in such situations where trans-venous pacing is likely to be delayed .
Message from this case
Cardiology’s ultimate moment of glory and truth is experienced when a life is saved with a pacemaker.
Extreme bardycardias are often fatal , but here is a patient with dangerously low heart rate , still not resulting in asystole or brady induced VT/VF . We had adequate time to plan a strategy . Severe bradycardias need not result in cardiac arrest always. Some hearts have amazing capacity and their fighting spirit amazes us ! .It should be noted that , the above example may be an exception than a rule .