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NBME 20 Answers

nbme20/Block 2/Question#23

Which of the following changes in the ...

Increased basal systolic blood pressure

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The way I approached the question was to consider what happens 1. When you grow from a baby to a child, and 2. when you grow from a teenager to an older adult. Whatever remained true between both of them was the right answer.

Right answer: The resting BP of a newborn is 65/40 (google), while that of a 1-month old is 95/60. The average adult is higher, with the American Heart Association citing (absurdly, IMO) that "normal" is <120/<80. Nevertheless, the trend is that BP increases as we age, whether we are newborns or old people.

Wrong answers: Development of coronary atherosclerosis: Perhaps due to the American diet it can be argued that the development of atherosclerosis is almost inevitable as you become an older adult. Certainly not true as a baby --> child.

Development of mitral stenosis: Similar reasoning as coronary atherosclerosis; you MAY develop it as an adult (not nearly as common as a buildup of atherosclerotic plaques), but sure, let's say that it can happen. Not true as a baby --> child.

Increased basal heart rate: The opposite is actually true. The basal heart rate of a newborn can easily exceed 150, and that's considered normal. As we age, this heart rate goes down.

Increased cardiac muscle mass: This one was the hardest to work through. It is true that as we age from a baby --> child our heart grows in size. But if we tweak our assumption from before with the American diet, and instead put our patient on a more moderate diet, realistically his heart shouldn't increase in size too much, at least to the point of cardiomegaly.

Increased compliance of arteries: As we become older adults, the compliance of arteries decreases and stiffness increases (careful not to confuse arteries with lungs, which actually do increase in compliance as we age!)

 +0  upvote downvote
submitted by ergogenic22(123),

aging results in increased arterial stiffness (change in Extra Ccellular Mmatrix composition - decreased elastin, increased collagen deposition); ISH is responsible for 60-80% of HTN cases in patients > 60. Also, decreased compliance as a result of aging causes increased pulse pressure

rio19111  why not dev. of coronary atherosclerosis? +1  
pakimd  @rio19111 i think the Q stem is asking in absence of any lesions of blood vessels; the number and severity of which increase with age. So with normal aging SBP should increase in isolation which may then result in the development of coronary atherosclerosis- if that makes sense +  
chandlerbas  aging causes decreased compliance in large arteries: (1) accumulation of collagen and calcium (2) degraded elastin and large arteries accumulation and it also may have something to do with lipofuschin +  

 +0  upvote downvote
submitted by mbourne(18),

Although everyone's arteries WILL get stiffer as we age, every single person will not develop coronary atherosclerosis and mitral stenosis. Will the valves become a bit stiffer? For sure! Will they develop "mitral stenosis"? No, that is not congruent with "normal aging".

"Isolated systolic hypertension, an elevation in systolic but not diastolic pressure, is the most prevalent type of hypertension in those aged 50 or over, occurring either de novo or as a development after a long period of systolic‚Äźdiastolic hypertension with or without treatment. The increase in blood pressure with age is mostly associated with structural changes in the arteries and especially with large artery stiffness."

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805932/