Brief Answer:
I would explain as follows:

Detailed Answer:
Hello XXXXXXX

Welcome on HCM!

I passed carefully through your recent medical history and would say that a dual chamber pacemaker (DDDR) is quite adaptable to higher cardiac output demands and can adjust the heart rate accordingly.

As the pacemaker varies the heart rate in accordance to the level of physical exertion due to the default algorithm (max heart rate around 220 - age), 140 bpm is quite fine.

But, remember that in physically well-fitted individuals, cardiac output demands may be accomplished to lower heart rate levels, and the responsible pacemaker sensor may just catch the difference.

Now, returning to your concrete problem, I would explain that your unsatisfactory physical performance may be explained in several ways.

(1) First it is necessary to investigate your physical conditioning level; that is the ability of your body muscles to cope with physical strain.

Skeletal muscles are responsible for producing the feeling of body weakness and tiredness at a certain exercise level.

This may be caused by lactic acid and other stimulating radicals accumulated in exercising muscles.

More trained a person is, lower and later comes this limiting sensation.

All the above may be explored by an exercise cardiac stress test, which investigates direct cardiac and skeletal muscle responses to physical activity; defines exercise capability, heart rate and blood pressure response. It may be coupled for a further study with oxygen saturation and even dosing of lactic acid blood levels.

(2) Independently to pacemaker functioning, cardiac function may be impaired to such a level that may limit your physical activity.

Sometimes, even frequent pacing may lead to some degree of cardiomyopathy.

This may be clarified by performing a cardiac ultrasound exam (echo), which offers evidence of overall cardiac structure, your LVEF, associated possible valvular dysfunctions, measures pulmonary pressures and vascular resistances.

(3) Other concomitant disorders may be responsible for your limited physical ability;

- a possible pulmonary dysfunction (a chest X ray study, a pulmonary function test and arterial blood gas analysis test could clarify this issue),

- a possible anemia (a complete blood count would rule in/out this option),

- several metabolic and endocrine disorders should be excluded (diabetes by fasting glucose test, thyroid dysfunction by thyroid function tests, chronic inflammation by PCR, ESR, etc., chronic renal disorder by renal function tests, etc).

So, to conclude, to make it clear and concise for you, I would summarize that, as you pacemaker is confirmed to function properly, according to your age, other tests should be done to find the reason of your complaints:

- exercise stress test,
- cardiac echo,
- chest X ray study,
- pulmonary function test,
- arterial blood gas analysis,
- fasting blood glucose,
- thyroid function tests,
- renal function tests, etc.

You need to discuss with attending physician about the above mentioned option.

Hope to have been helpful to you!

In case of further uncertainties, feel free to ask me at any time.

Kind regards,

Dr. Iliri

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