Dear Boathouse Doc,

I am a master coach who has several rowers who have abnormal heart rhythms called atrial flutter and atrial fibrillation.  What should I be aware of in terms of their training and will they be able to race in the spring?

Northeast Masters Coach.

Dear Coach,

I spoke with several cardiologist friends of mine regarding your question, and this is the consensus of their opinions.
 
The rhythms you mentioned are supraventricular tachycardias (rapid heart rates of the right and left atriums), which may be related to their rowing activities.  The heart is divided into four chambers, two atria and two ventricles.  These chambers contract in a coordinated manner to send blood to the lungs (right atrium and ventricle) and the body (left atrium and ventricle).  The arrythmias your rowers have are actually fairly common in the athletic population. 

In order for a rowing athlete to be successful, they have to be able to deliver a large amount of oxygen to the muscles.  The ability to deliver is referred to as cardiac output, or simply put; it reflects the total horsepower available in an individual.  Cardiac output is determined by heart rate each minute multiplied by the stroke volume for each heartbeat (amount of blood pumped).  The maximum heart rate per minute is determined by subtracting the individual’s age from 220.  For example, a 45-year-old master rower would have a maximum heart rate of 175 beats per minute (220 – 45 = 175).  In the untrained athlete, the cardiac output increases primarily by increases in the heart rate.  However, the conditioned athlete demonstrates changes in his or her heart which reflect the ability to pump more blood with each stroke, i.e. increased size of the cardiac chambers, some increase in the left ventricular wall thickness and increased ventricle filling time with the slower heart rate.  In order to increase the effectiveness of each beat, the stroke volume has to increase because the maximum heart rate is relatively fixed.

In your athletes with atrial flutter and fibrillation, their smaller chambers are contracting in a very rapid and disorganized manner, and thus they are not able to fill their ventricles fully and thus their cardiac output falls up to 20-30%, when they maintain a normal ventricular heart rate. As a result, they are not able to maintain their usual performance levels. 

Your athletes with this problem must have a complete cardiac workup to identify any underlying heart pathology that may cause this problem, such as coronary artery disease.  This generally would include an EKG, stress test and thallium scan.  On occasion, a 24-hour cardiac monitor might be indicated.  They probably will have their blood thinned in order to prevent the possibility of a stroke, as well as take heart medication to try to control the abnormal rhythm. Sometimes, they may have their heart shocked in order to force it into a normal rhythm (cardioversion). There has also been increased enthusiasm in the use of heat ablation of some of the nerves entering the heart in order to maintain a normal rhythm.

If your rowers have achieved a normal rhythm and have no underlying heart disease, they can be expected to perform normally and race without difficulty.  However if a rower is unable to maintain a normal rhythm, but has a normal heart rate, their performance will diminish due to the drop in their cardiac output.  They are not able to respond with a stepwise increase in the heart rate in response to the rowing intensity.  Instead they tend to peak their heart rate quickly, their anaerobic threshold is decreased and they will not mobilize lactic acid as efficiently as they could prior to developing the arrhythmia.   Those in atrial flutter and fibrillation will be able to row at a steady-state pace without much difficulty, but their erg splits will be somewhat higher.  They will have more significant problems racing, again related to their decreased cardiac output.

If your rower complains of a racing heart, chest pain, shortness of breath, or increased distress with exercise, they should immediately be taken to the hospital and evaluated, and if necessary treated.  This problem generally affects males over 40, and its incidence increases with age.  Your master athletes with athletic hearts and a normally low heart rate may be susceptible to this affliction.  If their work-up shows no abnormalities, they should be allowed to row within the limitations of this condition.

Boathouse Doc