Hi:
"I told him he should probably call a doctor."
Excellent advice.
"But he is a stubborn fellow and said he didn't want to make any hasty moves, and that he would wait and see if it got worse."
Sometimes the "wait and see" approach can work in the patient's favor, and other times it may/can prove deleterious or even fatal.

While I don't recall what you have specifically described has been posted about here in the past, some individuals have experienced a vibration, or buzzing feeling/sensation in the chest/thoracic area, which always warrants checking for possible problems that can involve the heart's electrical conduction system, i.e., irregular heartbeat/arrhythmia or a heart valve.
Also, in some individuals, as applicable, more so if there is a bounding, firm, or strong pulse (for whatever reason, constant or briefly), they can see a rhythmic pulsing or throbbing (in-sync with the heartbeat) in a vein, such as in the hand, arm, or neck, simply because of their body habitus, e.g., thin or thin 'n tall build (or so-called being "thin-skinned") and physique. A pulsing in the chest, and sometimes the abdomen/stomach, may/can be notcied as well.
Additionally, of the different types/kinds of heart conditions, various symptoms may/can be acute (occurring suddenly), be chronic (occurring over a long period of time), come and go (be transient, fleeting or episodic,
such as an irregular heartbeat, requiring the use of Holter monitor or event recorder at home and during daily activities) or even be silent.
Best of luck down the road of life to your friend and you.
Take care,
CardioStar*
WebMD member (since 8/99)

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Heart Disease TYPESMen and Women
Acquired in life or congenital (born with it)http://www.webmd.com/heart-disease/heart-disease-men
Heart disease SYMPTOMShttp://www.webmd.com/heart-disease/guide/heart-disease-symptoms Mayo Clinic
Heart DiseaseDefinition. Symptoms. Causes. Risk factors. Complications. Tests and diagnosis. Prevention......
Heart disease is a
broad term used to describe a
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http://www.mayoclinic.com/health/heart-disease/DS01120 LEARN ABOUT the Heart

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The Heart: (Human Anatomy) Pictures, Definition, Location in the Body and Heart Problems
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