CE: Namrta; JCM/201761; Total nos of Pages: 6;
JCM 201761
Original article
M-mode echocardiographic values in a cohort of young healthy individuals Alon Grossmana,b, Michal Benderlyc,d, Alex Prokupetza, Barak Gordona and Ofra Kalter-Leibovicic,d Objectives To determine normal M-mode values in healthy young adults and to evaluate whether these values differ among those in whom echocardiography was performed routinely and those in whom echocardiography was performed based on clinical grounds. Methods A cross-sectional study evaluating a large cohort of young academy applicants of the Israeli air force in the years 1994–2010. Studies were divided into those performed routinely and those performed because of abnormal ECG or physical examination findings. Echocardiographic variables were compared between the two groups and values are expressed as mean W SD. Results Echocardiography was performed routinely in 3525 applicants (age 18.5 W 1.0 years) and following a clinical referral in 3517 applicants (age 18.2 W 0.9 years). Those in whom echocardiography was performed routinely had slightly higher left ventricular end-systolic diameter (31.2 W 3.3 vs. 30.7 W 3.4 mm; P < 0.0001) and aortic root diameter (28.5 W 2.1 vs. 27.9 W 2.2 mm; P < 0.0001), and slightly lower left ventricular mass index (108.8 W 15.8 vs. 109.9 W 16.5 g/m2; P U 0.005). No differences were noted
Introduction Echocardiography is a common modality for evaluation of structural abnormalities of the heart and is used both for the evaluation of clinical findings and for screening purposes.1,2 Despite its extensive use in the general population, relatively few studies evaluated the normal echocardiographic parameters among young individuals. Normal values for echocardiographic measurements are based on data collected from relatively small cohorts3,4 or were determined in the 1970s and early 1980s.5,6 Since then, significant technologic improvements make it now possible to obtain direct digital measurements and to place the M-mode beam more accurately so that the measurements obtained are probably more accurate than those obtained in the past. The few studies that evaluated normal values of M-mode measures in recent years were performed in relatively heterogeneous populations,7–9 making it difficult to apply their findings to young healthy individuals. It is particularly important to set normal echocardiographic values for young adults as they frequently undergo echocardiography as a part of the evaluation prior to participation in competitive sports. 1558-2027 ß 2013 Italian Federation of Cardiology
between the two groups in left atrial diameter, left ventricular end-diastolic volume, posterior wall thickness and interventricular septum thickness. Conclusion Certain M-mode characteristics may differ (although to a slight degree) in young healthy individuals with electrocardiographic and physical findings compared with those with normal physical examination and electrocardiography. J Cardiovasc Med 2013, 14:000–000 Keywords: echocardiography, medical decision, screening making a The Israeli Air Force Aero Medical Center, Tel Hashomer, bDepartment of Internal Medicine E, Rabin Medical Center, Beilinson Campus Affiliated to Tel Aviv University Sackler Medical School, Petah Tikva, cUnit of Cardiovascular Epidemiology, The Gertner Institute for Epidemiology and Health Policy Research, Tel Hashomer and dSackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
Correspondence to Alon Grossman, MD, Rabin Medical Center, Beilinson Campus Affiliated to Tel Aviv University, Petah Tikva, Israel E-mail:
[email protected] Received 3 April 2013 Revised 19 May 2013 Accepted 4 June 2013
Morphologic echocardiographic abnormalities are poorly predicted by ECG and physical examination findings.10 Yet, the association between ECG and physical examination and M-mode characteristics has not been studied previously. This study evaluated a large cohort of young healthy nonprofessional athletic adults in an attempt to set the normal values of M-mode echocardiographic measures for this population and to compare echocardiographic variables between individuals referred to echocardiography based on clinical suspicion and individuals in whom echocardiography was performed routinely.
Methods Study population
The study population consisted of 17–25-year old male voluntary flight academy applicants. All applicants were previously screened to exclude significant medical conditions, including cardiovascular and respiratory diseases. All applicants with BMI greater than 30 kg/m2 are disqualified from flight academy, and thus were excluded from the study. Applicants were evaluated by an aero medical physician at the Israeli air force aero medical DOI:10.2459/JCM.0b013e3283641bf0
CE: Namrta; JCM/201761; Total nos of Pages: 6;
JCM 201761
2 Journal of Cardiovascular Medicine 2013, Vol 00 No 00
center. This evaluation included medical history, physical examination and a 12-lead resting ECG. All applicants underwent echocardiography prior to enlistment. Those in whom physical findings, medical history or ECG findings raised suspicion of the presence of cardiac disease underwent diagnostic echocardiography (these will be referred to from here on as ‘clinical group’). Applicants who had no clinical indication for performance of echocardiography underwent routine echocardiography following a nonmedical selection process, which lasted approximately 4–6 months (these will be referred to from here on as ‘routine group’). All echocardiographic studies in which morphologic abnormalities were identified were excluded from the analysis.
study the differences in combinations of M-mode characteristics identified by principal component analysis between the two groups of participant, adjusted for age, BMI, heart rate, pulse pressure and SBP. The percentage of variability in predicted combination explained by clinical findings and covariates was computed as the ratio between the trace of the sum of square and cross-product matrix associated with an effect and the trace of the covariance matrix of M-mode characteristic combination. Differences in aortic root diameter between the two groups were assessed by analysis of covariance adjusting for the same covariates described above. Data were analyzed with the SAS software version 9.2 (SAS Institute, Cary, North California, USA).
Echocardiography studies
We reviewed all routine echocardiographic studies of aircrew applicants performed at the Israeli air force aero medical center between January 1994 and January 2010. All echocardiographic studies were obtained with one of three devices (HP 500 SONOS, ATL 5000HDI and PHILIPS HD 11 XE). Second generation devices (HP 500 SONOS and ATL 5000HDI) were used from 1994 to 2008. A third generation device (PHILIPS HD 11 XE) was used from 2008 onward. All studies were performed by one of three experienced technicians and interpreted by one of two cardiologists specialized in echocardiography. Transthoracic echocardiography included twodimension, M-mode and Doppler studies performed according to the American Society for Echocardiography guidelines for obtaining images, quantification of chamber dimensions and assessment of valvular disease.11–13 All studies were performed in four windows (left and right parasternal long axis, parasternal short axis and apical four chamber view). In cases in which elevated pulmonary artery SBP or tricuspid regurgitation was suspected based on these four windows’ evaluation, a subcostal window is added. Measurements were corrected for body surface area. Left ventricular mass (LVM) was estimated as 1.05 [(left ventricular enddiastolic diameter (LVED) in mm þ posterior wall thickness in mm þ intraventricular septum, in mm)3 LVED3]/1000. Left ventricular mass index (LVMI) was calculated as LVM/BSA. The study was approved by the ethics committee of the Medical Corps of the Israel Defense Force (IDF-685–2007).
Results Echocardiography was performed routinely in 3525 applicants (‘routine group’) and following clinical referral in 3517 applicants (‘clinical group’). Demographic and clinical characteristics of the two groups are presented in Table 1. Applicants in the ‘routine group’ were, on average, 3.6 months older, had slightly higher weight and BMI at baseline examination, and slightly lower (but not statistically significant) DBP and heart rate. Normal distributions of posterior wall thickness, interventricular septal (IVS) thickness and LVMI are presented in Figs. 1–3. Echocardiographic findings of the entire cohort are presented in Table 2. Only left ventricular end-systolic volume (LVES), aortic root diameter and LVMI were different between the two groups. Left atrial diameter, posterior wall thickness, IVS thickness and LVED volume were similar between the two groups. Principal component analysis of the M-mode characteristics revealed three components: parameters related to heart volume including left atrial diameter, LVES volume and LVED volume; parameters related to LVM including posterior wall thickness, IVS and LVMI, and aortic root diameter (single variable). In multivariate analysis, using multivariate analysis of covariance, clinical attributes explained only 0.15% of the variability of the parameters related to heart volume and only 0.12% of the
Table 1
Demographic characteristics of study populationa
Statistical analysis
Continuous variables are presented as mean SD. Comparisons between individuals who underwent a clinical vs. those who underwent a routine test were tested with analysis of variance or the Welch test, where appropriate. To find combinations of M-mode characteristics that were closely related, we performed exploratory principal component analysis with Varimax (orthogonal) rotation. Next, multivariate analysis of covariance was used to
Age (years) Height (cm) Weight (kg) BMI (kg/m2) SBP (mmHg) DBP (mmHg) Heart rate (beats/min) a
Routine group N ¼ 3525
Clinical group N ¼ 3517
P value
18.5 1.0 176.4 6.2 68.5 8.5 22.0 2.3 123.7 12.0 69.9 9.0 72.0 13.8
18.2 0.9 176.7 6.5 67.5 8.6 21.6 2.3 123.2 13.1 70.2 9.6 73.9 14.6
