Outer Limits of Physiologic Hypertrophy and Relevance to the Diagnosis of Primary Cardiac Disease

Imaging of cardiopulmonary diseases

Clear physiologic adaptations to endurance and resistance training occur in the myocardium. These morphologic changes have been identified primarily by echocardiography. In the evaluation of the symptomatic athlete, imaging is a valuable tool. To differentiate athletic hypertrophy from hypertrophic cardiomyopathy, echocardiography, or MRI may be used, although the latter may be superior in the accurate assessment of wall thickness. Either imaging modality may be used to differentiate athletic dilatation from dilated cardiomyopathy in which systolic dysfunction always accompanies the dilatation. To exclude anomalous coronary arteries, either MRI or CT is a reasonable examination, although the latter requires x-ray exposure and iodinated contrast dye. Chest radiograph continues to be the standard imaging modality for athletic lung disease, whereas fluoroscopy and laryngoscopy are useful for identifying vocal cord dysfunction. Knowledge of the utility of these different imaging modalities is crucial to the practitioner of sports medicine.

Cardiac risk factors and participation guidelines for youth sports

Accurate assessment of the cardiac system in pediatric and adolescent youth is important. The hemodynamic demands associated with exercise, training, and sport participation are usually positive and beneficial; however, when an underlying cardiac problem exists, it is imperative that such cardiac problems be identified. Safe sport-related cardiac participation guidelines should be provided for young athletes and their families and coaches. This chapter provides a physician perspective on the recognition and current cardiac management considerations for young athletes participating in both static and dynamic types of sports. The most recent guidelines for hypertension in youth are also provided.

Effect of endurance training on cardiac morphology in Alaskan sled dogs

The cardiac morphology of 77 conscious Alaskan sled dogs before and after 5 mo of endurance training (20 km/day team pulling a sled and musher) was studied using two-dimensional and M-mode echocardiography. Subgroups included dogs with at least one season of previous training ("veterans") and dogs undergoing their first season of training ("rookies"). Training resulted in a significant (P < 0.05) decrease in resting heart rate (-15%) and significant increases in interventricular septal thickness (systole, 15%; diastole, 13%), left ventricular (LV) internal dimension in diastole (LVIDd, 4%), LV free wall thickness in systole (9%) and diastole (LVWd, 9%), and left atrial diameter (5%) in all dogs, but the increase in LVWd was greater in rookies (16%) than in veterans (7%). Training increased end-diastolic volume index (8%), LV mass index (24%), and heart weight index (24%) and decreased the LVIDd-to-LVWd ratio (-6%) but did not alter cardiac index. We conclude that increased LV mass attributable to LV dilation and hypertrophy is associated with endurance training in Alaskan sled dogs. Disproportionate LV wall thickening accompanying LV dilation suggests that cardiac morphological changes are due to volume and pressure loading. These training-induced changes are similar to those documented in human athletes undergoing combined isometric and isotonic training and differ from studies of dogs trained on treadmills.

The athlete's heart

We have provided an overview of the athlete's heart, focusing on the young athlete. Primary caretakers of athletes should know the major causes of exercise-related cardiac complications and sudden cardiac death and look for these conditions during preparticipation evaluations. We strongly suggest that coaches and other athletic personnel be required to learn basic life support measures such as cardiopulmonary resuscitation (CPR) and to update their skills on an annual basis. Such efforts will help prevent additional exercise-related cardiac deaths.