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From the clinical description which you have given, it sounds like there is some rhythmic disorder or conduction defect in heart. EKG, just gives a rough idea about them. So, It has to be ruled out or confirmed by further investigations like echocardiogram
etc. This is the reason your doctor would have advised for further evaluation. But, sudden very hoarse voice, very bad tightness in chest is of much concern now and I suggest you to see Cardiologist ASAP. Let me know if you have have any clarifications.
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