Hypertensive heart disease (HHD) is a consequence of the increased demands placed on the heart by hypertension, causing pressure overload and ventricular hypertrophy. As discussed in Chapter 10, hypertension is a common disorder associated with considerable morbidity and affecting many organs, including the heart, brain, and kidneys. The comments here will focus specifically on the major cardiac complications of hypertension, which result from pressure overload and ventricular hypertrophy. Myocyte hypertrophy is an adaptive response to pressure overload; there are limits to myocardial adaptive capacity, however, and persistent hypertension eventually can culminate in dysfunction, cardiac dilation, CHF, and even sudden death. Although hypertensive heart disease most commonly affects the left side of the heart secondary to systemic hypertension, pulmonary hypertension also can cause right-sided hypertensive changes—so-called “cor pulmonale.” http://ebooksmedicine.net
Fig. 11.15 Pathwaysintheprogressionofischemicheartdiseaseshowingtherelationshipsamongcoronaryarterydiseaseanditsmajorsequelae.CORONARY ARTERY DISEASE Chronic ischemic heart disease Congestive heart failure Myocardial ischemia Acute plaque change; coronary artery thrombosis MYOCARDIAL INFARCTION with muscle loss and arrhythmias Ventricular remodeling Infarct healing Hypertrophy, dilation of viable muscle Myocardial ischemia of increased severity and duration SUDDEN CARDIAC DEATH
The criteria for the diagnosis of systemic hypertensive heart disease are (1) left ventricular hypertrophy in the absence of other cardiovascular pathology (e.g., valvular stenosis), and (2) a history or pathologic evidence of hypertension. The Framingham Heart Study established unequivocally that even mild hypertension (above 140/90 mm Hg), if sufficiently prolonged, induces left ventricular hypertrophy. Roughly 25% of the U.S. population suffers from at least this degree of hypertension.
Asdiscussedearlier,systemichypertensionimposespressureoverloadontheheartandisassociatedwithgrossandmicroscopicchangessomewhatdistinctfromthosecausedbyvolumeoverload.Theessentialfeatureofhypertensiveheartdiseaseisleftventricularhypertrophy,typicallywithoutventriculardilationuntilverylateintheprocess(
Fig.11.16A ).Theheartweightcanexceed500g(normalfora60-to70-kgindividualis320to360g),andtheleftventricularwallthicknesscanexceed2.0cm(normalis1.2to1.4cm).Withtime,theincreasedleftventricularwallthicknessimpartsastiffnessthatimpairsdiastolicfillingandcanresultinleftatrialdilation.Inlong-standingsystemichypertensiveheartdiseaseleadingtocongestivefailure,thehypertrophicleftventricletypicallyisdilated.
Microscopically,thetransversediameterofmyocytesisincreasedandthereisprominentnuclearenlargementandhyperchromasia(“boxcarnuclei”),aswellasintercellularfibrosis(seealso
Fig.11.1D