Electro and Echocardiographic Profile of Young American Navy Recruits Presented with Syncope

Background: The etiology of syncope in young adults is poorly defined and most studies reveal benign etiologies. However, case reports suggest that exercise-related syncope, even in young patients, can be a harbinger of sudden cardiac death. We aim to determine the characteristics of young adults presenting with syncope in a diverse population of navy recruits. Methods: A retrospective chart review was performed on all Navy recruits who presented with a complaint of syncope to the Captain James A. Lovell Federal Health Care Center (JALFHCC) between June 1, 2006 and May 31, 2013. There was a total of 154 charts. Demographics and clinical data, along with Electrocardiogram (EKG), telemetry, and echocardiographic findings were recorded. Variables were compared between the subjects with abnormal cardiac profile and subjects with normal cardiac results. Results: The sample size of 154 included 95 males and 59 females. There were 13 (8.4%) subjects who were found to have concerned cardiac findings; 9 were males (9.5% of males) and 4 were females (6.8% of females). Compared to those without cardiac findings, there were no significant differences in age (20.2 ± 3.8 vs. 20.2 ± 2.5 years), body mass index (25.8 ± 2.8 vs. 24.7 ± 3.5), prior history of syncope (23 vs. 21%), or presence of exertional syncope (77 vs. 63%). Conclusion: A significant proportion of young American navy recruits have evidence of concerning electro and echocardiographic findings. We did not find any clinical profile predicting such findings although there was a statistically insignificant, but noticeable trend towards exertional syncope in those who had concerning cardiac abnormalities.


Introduction
Syncope is a prevalent medical condition that accounts for 3.5% of all emergency room visits and 1 to 6% of all hospital admissions annually in the United States [1]. Syncope is defined as a sudden and temporary loss of consciousness associated with concurrent loss of postural tone secondary to a reduction of cerebral blood flow followed by restoration to a normal physiological state [2]. Since the subjects of syncope often cannot recall the events leading to their altered mental state, the etiology of syncope in the young and elderly remains a diagnostic challenge and the source of ongoing research [3]. Syncope can occur in any age group although the elderly usually undergoes more extensive diagnostic evaluation as the likelihood for finding cardiac pathology is higher and they have more documented comorbid disease [4,5]. Conversely, the etiologies of syncope in the young remain poorly characterized with most of the literature focusing on benign conditions such as psychiatric and neuro-cardiogenic causes [2,[4][5][6][7][8]. Ganzeboom et al. elucidated the different triggers of syncope in 394 medical students of both genders and discovered that a warm environment, prolonged standing, pain, illness, and alcohol represent some of the triggers for syncope [9]. More importantly, O'Connor et al. have also reported exertion-related syncope in young athletes with and without history of cardiac disease leading to sudden cardiac death [7]. These findings may suggest that syncope, most commonly exertional in nature, may not be limited to benign causes in the young population especially amongst patients with underlying heart conditions such as hypertrophic cardiomyopathy and a history of strenuous exercise.
Nearly 60% of syncope cases that interfere with activities of daily living in the young require adequate study [10,11]. We studied young American navy recruits who presented in the inpatient or outpatient settings. This group of subjects was thought to be ideal as they are trained for jobs requiring a high level of physical fitness. Also, the nature of their occupation mandates a standard of frequent detailed objective evaluation.

Methods
The study is a retrospective chart review examining navy recruits and students who presented to Captain James A. Lovell Federal Health  Demographic data was recorded including age, race, gender, body mass index [BMI], prior history of syncope, exertional vs. nonexertional nature, and prior history of syncope. Patients were categorized into two groups; concerning cardiac findings and nonconcerning cardiac findings based on a cardiac evaluation by a consulting cardiologist. Variables of these 2 groups were compared.

Statistical Analysis
Statistical analysis was performed on IBM SPSS Statistical program [version 22, IBM Corporation, Pittsburgh, PA]. Statistical analysis consisted of computation of means and standard deviations for continuous variables and frequencies for categorical variables. Differences in continuous variables between the two study groups were analyzed by independent sample t test. Differences in categorical variables were analyzed by chi-square test or Fisher's exact tests as appropriate. A two-sided alpha error of p ≤ 0.05 was considered statistically significant.

Results
Over the 7-year period, 150 navy recruits and 4 students met the inclusion criteria. The mean age was 20.2 ± 2.62 years. There were more males (95) than females (59); males were significantly taller and had greater body weight than females. More females had prior history of syncope (30.5%) than males (15.8%), There were no statistically significant differences between genders in age, BMI, and presence of exertional syncope (Table 1).   There were 13 subjects (8.4%) who had concerning cardiac abnormalities. Characteristics of patients with concerning cardiac findings compared to those without concerning cardiac findings are summarized in Table 2. Subjects with concerning cardiac findings had greater body weight with no significant differences in age, height or BMI. The details of patient characteristics and concerning cardiac abnormalities are listed for each of the 13 subjects in Table 3. There was a trend toward more exertional syncope in those who had concerning cardiac abnormalities.

Discussion
We find a trend suggesting patients with exertional syncope tended to have concerning cardiac findings that included early repolarization and RBBB, hyperdynamic LV function, mildly dilated right ventricle, sinus bradycardia, right axis deviation, right ventricular hypertrophy, left posterior fascicular block, Atrial Fibrillation, prolonged QT interval, tricuspid regurgitation, mitral regurgitation, pulmonary regurgitation, WPW, LBBB, junctional rhythm, and sinus pauses. Though this trend did not reach a statistically significant level. Da Costa et al. studied 329 patients with syncope who underwent electrophysiology study [EPS] and found that ECG abnormality was the only predictive variable associated with a significant arrhythmic event in patients with episode of syncope and a negative EPS [11].
Syncope cannot be ignored particularly in subjects employed in jobs which are high-risk and physically demanding activities for e.g. pilots, drivers, machine operators, and military personnel. Evaluation of such patients can be very costly; therefore, risk stratification and case selection are crucial to provide cost effective management. Clinical history can be helpful in selecting those young adult subjects for further evaluation who have syncope during exercise or who have a family history of syncope, sudden death, myocardial disease, or arrhythmias [11].
In our study we compared subjects with concerning cardiac findings to those without concerning cardiac findings and noted no statistically significant differences in age, BMI, prior history of syncope, or exertional syncope. Although we do acknowledge the sample size as being possibly inadequate to detect such an effect if one exists.  One of the strengths of our study was all patients who presented with syncope were evaluated for arrhythmic disorders and structural heart disease. The occurrence of concerning cardiac findings, however, did not necessarily specify that syncope was caused by a cardiovascular disorder. We acknowledge several weaknesses in our study. The sample size was underpowered. The arrhythmias or structural heart diseases that were detected may not have a causal or contributory relationship with the syncopal event although there was no evidence to the contrary either. The diagnostic evaluation performed may have been more rigorous owing to the nature of subjects' duties, so results can only be generalized to the population at large with caution. Other limitations include a lack of data on cardiac assessments done prior to enrolling in the navy. Of note the nature of a single-center study design prohibits the generalizability of results. Also, of note our study examines the relationship of syncope with cardiac etiologies in young adult subjects. Further studies on this clinical question are warranted to enable correlation between such cardiac findings and significant mortality and morbidity in the context of syncopal events.

Conclusion
A significant proportion of young American navy recruits have evidence of concerning electro and echocardiographic findings. The clinical profile of young subjects presenting with syncope is variable. Although there was a statistically insignificant, but noticeable trend towards exertional syncope in those who had concerning cardiac abnormalities. Larger-scale studies are necessary to reflect the reproducibility of these results.

Conflicts of Interest
There are no conflicts of interest for the present study.