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Hamilton and Norwood described the degrees of severity of MPB from a mild Type I to a severe Type VII3,4 (Fig. 256-2). Fortunately, a large majority of male patients do not progress past Types VI: Norwood found that at age 79 only 11% of men have Type VII MPB (Table 256-1), and Unger found that among men older than 65 only 13.7% have Type VII MPB5 (Table 256-2). Thus, if one treats all or most patients as if they will develop Type VI MPB, one is being reasonably cautious. An exception is for cases with a family history of Type VII MPB, in which case it is wiser to assume an evolution to Type VII MPB.
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