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2AGING AND THE HEARTC. Biochemical ChangesThese changes include decreased protein elasticity, changesin enzyme content that affect metabolic pathways,decreased catecholamine synthesis, and diminishedresponsiveness to beta-adrenergic stimulation.D. Electrical Conduction SystemSubstantial loss of pacemaker cells in the sinus node cause afall in heart rate and finally failure. This condition is calledsick sinus syndrome and is the most common reason forimplanting an electronic pacemaker. Increased fibrosisand calcification of the conduction system and loss ofspecialized cells in the His bundle and bundle branches canresult in failure of the electrical impulse to reach theventricles. This condition is called heart block and requiresa pacemaker. (See the chapter Pacemakers.)E. Valvular ChangesThese changes include fibrosis, thickening and calcificationof heart valves which leads to degenerative valvular disease.Calcified aortic stenosis may require valve surgery butthe statins, cholesterol-lowering agents, have been shownto decrease the rate of stenosis and may delay surgicalintervention. Mitral annular calcification occurs commonlyand occasionally causes mitral regurgitation, atrialarrhythmia, heart block, and infective endocurditis.Fibroproliferative lesions producing mitral regurgitationhas occured in elderly patients treated with antiparkinsoniandopamine receptor agonist pergolide.III. CARDIOVASCULAR THERAPYIN THE ELDERLYA. Thrombolytic TherapyPatients 70 years or older with an acute myocardial infarctare at high risk for serious events. Thrombolytic therapymay prevent death and further morbidity. Unfortunately,in patients older than 75 there is an increased risk ofintracranial bleeding. This excessive risk must be balancedagainst any possible benefit derived from thrombolytictherapy. The incidence of intracranial hemorrhage in thisage group is greater than 1.5% for alteplase (tissueplasminogen activator, t-PA) and tenectaplase, but greaterthan 0.5% for streptokinase.Although intracranial hemorrhage incidence is lowerwith streptokinase, it is not the drug of choice in NorthAmerica. Fortunately, in the UK, Europe, and worldwidethe less expensive agent streptokinase is still the mostwidely used pharmacologic reperfusion therapy. Thrombolyticagents that are effective but cause less intracranialbleeding than alteplase and tenectaplase in theelderly would be important additions to the therapeuticarmamentarium.B. Percutaneous InterventionBecause thrombolytic therapy carries a major risk ofintracranial hemorrhage and stroke in patients over age 75,randomized clinical trials have confirmed the beneficialeffects of primary coronary angioplasty with intracoronarystents. PCI is superior to thrombolytic therapy and ispreferred if skilled cardiologists and facilities are readilyavailable.In a randomized study of 87 patients older than 75 withacute myocardial infarction, the composite of death,reinfarction, or stroke at 30 days occurred in 4 (9%)patients in the percutaneous intervention (PCI) group ascompared with 12 (29%) in the patients receivingstreptokinase intravenously ( p ¼ 0.01). Patients olderthan 75 years of age with acute myocardial infarction orunstable angina obtain beneficial results with placement ofa stent in the culprit coronary artery, blocked by atheromaand thrombosis.C. Beta-Blocker TherapyBeta-adrenergic blocking drugs, beta-blockers, have provenbeneficial and save lives in patients with acute myocardialinfarction regardless of age. Some caution is requiredbecause the elderly over the age of 75 may have disease ofthe sinus node and slow heart rates may occur if the doseof the beta-blocking drug is excessive. Small doses ofthese agents are also beneficial in the elderly patientwith heart failure angina, atrial fibrillation, and hypertension.In the elderly hepertensive patient, a standing bloodpressure should always be taken to doucment posturalhypotension caused by vasodilatory anti-hypertensiveagents. Beta-adrenergic blockers do not cause posturalhypotension.D. Calcium AntagonistsThe calcium antagonists, or calcium entry blockers, arewidely used to treat hypertension. From 1990 to 2002, theWorld Health Organization (WHO) and the joint nationalcommittee for advice on hypertensive treatment in theUnited States recommended the use of calcium antagonistsas first line agents for management of hypertension in the