Hi friend,
Welcome to Health Care Magic

Yes, it could be...
Heart rate less than 60 is called slow – Bradycardia
40 is usually from block in the conduction system (nerves)–

HOLTER (24 to 48 hour ambulatory monitoring) is done to analyse and plan for further management

ECHOcardiogram is usually necessary to see the heart valves (muscle (Cardiomyopathy) and heart function (Ejection fraction, wall motion abnormality) / clots...     

TMT – Treadmill exercise ECG; may be with thallium isotope – is also routinely done to evaluate ischemia (reduced blood flow / Coronary Artery Disease)

If there are no clues, advanced investigation is necessary – Electro Physiological Studies (EPS) > it resembles angio – a catheter is put inside the heart / electrical activity recorded / stimulation and suppression tests are carried out / suitable medicine tested and so on. Though the test is the gold standard, it is INVASIVE) and is not generally done unless there are compelling indications. This super-speciality expert is called ELECTRO-PHYSIOLOGIST.

See a Cardiologist / get yourself examined / get investigated...
The treating doctor may suggest them depending on need, based on his assessment of the situation.
You may need a pacemaker...

Take care
Wishing speedy recovery
God bless
Good luck

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