From a case of hypertensive heart disease. In myocardial hypertrophy some nuclei are large and hyperchromatic reflecting increased DNA. Myofibers are widened but this finding, without objective validation, is not very reliable.
From the right ventricle of a newborn with pulmonary hypertension. Note “boxcar” nucleus in upper left region of photo.
Hypertrophy is the response of the myocardium to increased work. Changes in myocardial mass are not all bad, e.g., hypertrophy that occurs in fitness programs which produces a larger stroke volume allowing us to have a normally desired cardiac output during rest and exercise with a slower rate. Increased myocardial mass is due to increased size of myocytes and increased interstitial tissue. Overall heart size may or may not increase since hypertrophy may or may not be associated with dilation. Dilation is a much more prominent feature in response to volume overload than to pressure overload. In the latter, the walls may be thick with no dilation, 'concentric hypertrophy'; the ratio of chamber volume to wall thickness decreases. Though we measure the ventricular wall thickness as a reflection of the degree of hypertrophy, it is obvious that that measurement is not accurately reflecting myocardial mass in cases of hypertrophy with dilation, i. e., 'eccentric hypertrophy', in which the ratio of chamber volume to wall thickness may remain unchanged.