Understanding ECGs: bradycardias--fit and fitting
In the fourth article in our series Dominic Cox and Hamish Dougall look at bradycardias--their diagnosis, significance, and management
Symptoms from slowing of the heart can be very varied, from sudden death, recurrent syncope, and epileptic-type fits, to much milder symptoms, such as lethargy, breathlessness, etc. The history can be very revealing, but can also be very unreliable in those patients who truly lose consciousness. Some bradycardias are only intermittent problems with bothersome recurrent blackouts but no abnormality found after many years of medical investigation. Getting evidence of an intermittent problem can be very difficult.
Bradycardia is “slow” cardiac rhythm and results from either a failure of initiation of the heart beat or failure of passage of this electrical message through the heart--that is, normal sinus node “spark plug” activity is disturbed or there is interruption of the passage of this activity to tell the pump to work. This second type of failure usually occurs at the atrioventricular (AV) node.
The intrinsic rate of the sinoatrial (SA) node, which