Higher Heart Weight in New Zealand Māori and Pacific Islanders

Binucleated Myocytes and Heart Weight: A Preliminary Study Linking Cardiac Hypertrophy and Myocyte Hypertrophy

ABSTRACT

Hypertrophy of the heart is assessed by heart weight (and dimensions) and myocyte hypertrophy. Establishing an association between the two may be useful in assessing hypertrophy in cases where there are limitations in assessing the heart weight. This preliminary study explored the association between the number of binucleated myocytes (a feature of myocyte hypertrophy) in a randomly chosen single high-power field of the left ventricular free wall and heart weight in an adult White population. It also compared the number of binucleated myocytes between cases with increased heart weight (>400 g in female and >500 g in male) and cases with normal heart weight. Heart weight and number of binucleated myocytes correlated significantly in male only. Increased heart weight had a significantly higher number of binucleated myocytes, with 8.5 binucleated myocytes being able to segregate cases with increased heart weight (74% sensitivity and 79% specificity). The results of this study showed the number of binucleated myocytes may have a complementary role in assessing hypertrophy of the heart.

Significant difference in cardiac ventricular dimensions when measured using two different standard methods

Cardiac ventricular dimensions measured at postmortem examination are used to assess whether there is hypertrophy of the heart chambers. However, there is no clear consensus on where these measurements should be taken. Some have proposed this should be measured at the mid-ventricular level, but others advocate it should be measured at a set distance (e.g. 20 mm) from the base of the heart. Twenty consecutive adult hearts were examined and showed the ventricular dimensions were significantly higher (mean: 5-15 mm, p < 0.01) when measured at a level 20 mm from the base of the heart compared to the mid-ventricular level. Of clinical significance is that in slightly less than half the cases, normal ventricular dimensions at mid ventricle level fell within the criteria considered pathological (> 40 mm) when measured at 20 mm from the base of the heart. In terms of actual ventricular dimensions, only the left ventricle diameter measured at 20 mm from the base of the heart correlated significantly (albeit moderately) with heart weight, suggesting it can be a predictor for cardiac hypertrophy.

Estimating heart mass from heart volume as measured from post-mortem computed tomography

Heart mass can be predicted from heart volume as measured from post-mortem computed tomography (PMCT), but with limited accuracy. Although related to heart mass, age, sex, and body dimensions have not been included in previous studies using heart volume to estimate heart mass. This study aimed to determine whether heart mass estimation can be improved when age, sex, and body dimensions are used as well as heart volume. Eighty-seven (24 female) adult post-mortem cases were investigated. Univariable predictors of heart mass were determined by Spearman correlation and simple linear regression. Stepwise linear regression was used to generate heart mass prediction equations. Heart mass estimate performance was tested using median mass comparison, linear regression, and Bland-Altman plots. Median heart mass (P = 0.0008) and heart volume (P = 0.008) were significantly greater in male relative to female cases. Alongside female sex and body surface area (BSA), heart mass was univariably associated with heart volume in all cases (R² = 0.72) and in male (R² = 0.70) and female cases (R² = 0.64) when segregated. In multivariable regression, heart mass was independently associated with age and BSA (R² adjusted = 0.46-0.54). Addition of heart volume improved multivariable heart mass prediction in the total cohort (R² adjusted = 0.78), and in male (R² adjusted = 0.74) and female (R² adjusted = 0.74) cases. Heart mass estimated from multivariable models incorporating heart volume, age, sex, and BSA was more predictive of actual heart mass (R² = 0.75-0.79) than models incorporating either age, sex, and BSA only (R² = 0.48-0.57) or heart volume only (R² = 0.64-0.73). Heart mass can be more accurately predicted from heart volume measured from PMCT when combined with the classical predictors, age, sex, and BSA.

Prevalence of Abnormal Heart Weight After Sudden Death in People Younger than 40 Years of Age

Background After sudden cardiac death in people aged <40 years, heart weight is a surrogate for cardiomegaly and a marker for cardiomyopathy. However, thresholds for cardiomegaly based on heart weight have not been validated in a cohort of cases of sudden cardiac death in young people. Methods and Results We surveyed medical examiner offices to determine which tools were used to assess heart weight norms. The survey determined that there was no gold standard for cardiomegaly (52 centers reported 22 different methods). We used a collection of heart weight data from sudden deaths in the Northwestern Sudden Death Collaboration (NSDC) to test the 22 methods. We found that the methods reported in our survey had little consistency: they classified between 18% and 81% of NSDC hearts with cardiomegaly. Therefore, we obtained biometric and postmortem data from a reference population of 3398 decedents aged <40 years. The reference population was ethnically diverse and had no known cardiac pathology on autopsy or histology. We derived and validated a multivariable regression model to predict normal heart weights and a threshold for cardiomegaly (upper 95% CI limit) in the young reference population (the Chicago model). Using the new model, the prevalence of cardiomegaly in hearts from the NSDC was 19%. Conclusions Medical examiner offices use a variety of tools to classify cardiomegaly. These approaches produce inconsistent results, and many overinterpret cardiomegaly. We recommend the model proposed to classify postmortem cardiomegaly in cases of sudden cardiac death in young people.

Significant Differences in PostMortem Heart Weight Before and After Dissection Using the Short-Axis Dissecting Method

Correctly assessing heart weight can be critical at postmortem examination. The current international guidelines advocate using the short-axis method in dissecting the heart and the heart weighed when the blood is emptied. However, it did not specify at what point the heart should be weighed or how the blood should be emptied. This study compared heart weights at three different time points during the heart examination (immediately after dissecting out of the pericardial sac with blood still in chambers, blood washed/removed from heart chambers without the heart opened, and the heart completely opened, blood emptied, and pad dried). This was to illustrate the variation in measurement and potential errors when the heart is weighed at different time of dissection. The results show that there were statistical and clinical significant differences between the heart weights at each weighing points. We recommend the heart to be completely dissected with any blood and residual washing/rinsing water emptied before being weighed. Although performed in this study, the effect of pad drying the heart on heart weight was not explored and was a limitation in this study.