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The continuous cough
with out any infection in heart patients can be mainly due to 2 reasons:-
-if the working capacity of heart is reduced that is ejection fraction
of left ventricle is reduced then in such a patient there will be cough due to water getting filled in lungs and is medically called as congestive cardiac failure and this will happen more on exertion like walking;doing some work;climbing stairs etc.
-second reason for the cough if it is disturbing but not harming the health of a patient can be due to side effects of some medicines like Losartan/Telmisartan/Enalapril/Ramipril
which belong to group of ACE inhibitors and these drugs are used and are important to improve the functioning capacity of heart as well as to control hypertension
Please see and discuss the points i have suggested and in case if it is due to medicines then the Cardiologist may change the medicine or reduce the dose.And if it due to congestive failure then the doctor may increase the dose of or add a diuretic
to reduce the water and she should feel better.