As new classes of drugs like ACE inhibitors came along, Mr. Cheney benefited from them in combination with older ones like beta blockers, calcium channel blockers and more powerful diuretics.

While vice president, he developed additional problems, and each time he received the latest technology. For example, he had angioplasty to unblock coronary arteries; stents to keep them open; and surgery to repair aneurysms, or ballooning of arteries, behind both knees. A new combination device was implanted: a pacemaker to detect and correct abnormal heart rhythms, and a defibrillator to give a powerful electrical shock to stop potentially fatal ones.

Mr. Cheney even detected a flaw in the 25th Amendment to the Constitution that could have led to serious disruption if he had become incapacitated. Other than resignation, there is no way to remove a sitting vice president. If a stroke or a serious heart attack had left him unable to function (and unable to resign voluntarily), “I might stand in the way of the removal of a president unable to discharge his duties,” he wrote in his memoir — “or I might become an incapacitated acting president.”

So, shortly after his inauguration, Mr. Cheney wrote a letter of resignation and left it in his desk with instructions to a key aide: if he were to be incapacitated, give the letter to the president to decide whether to forward it to the secretary of state for action in accordance with the amendment’s provisions.

The defibrillator never discharged while Mr. Cheney was in the White House. But it did in 2009, in Wyoming, while he was backing his car out of his garage. And he had yet another heart attack, his fifth, in 2010 — just in time to benefit from a ventricular assist device, a battery-powered implant that helped his severely damaged heart pump enough blood to let him work, remain physically active and await a transplant. (The implant operation, at Inova Fairfax Hospital in Virginia, left him unconscious for weeks.)

The first human heart transplant was performed in 1967. Constant improvements since have made it possible to help even some people in their 70s, like Mr. Cheney. And while even the best care cannot prevent the inexorable progress of atherosclerosis in many patients, Mr. Cheney may not have run out of options. If his body rejects his new heart, he can try for a second.

Indeed, it is impossible to predict for how long the latest therapies will further extend Mr. Cheney’s life. Raymond J. Nelson, a Canadian home builder and philanthropist who at 79 received a new heart at the University of Alberta Hospital, lived with it for more than 10 years, dying in 2010 at 90. Dr. Reiner says it is not unreasonable for Mr. Cheney to expect to live another decade, a goal most doctors would have considered impossible a few years ago.