The spatial QRS-T angle outperforms the Italian and Seattle ECG-based criteria for detection of hypertrophic cardiomyopathy in pediatric patients

Is left bundle branch pacing (LBBP) associated with better depolarization and repolarization kinetics than right ventricular mid septal pacing (RVSP)? - Comparison of frontal QRS -T angle in patients with LBBP, RVSP and normal ventricular conduction

AIMS

To assess the frontal QRS- T angle (f QRS- T angle) in patients with left bundle branch pacing (LBBP) as compared to right ventricular mid septal pacing (RVSP) implanted for symptomatic high degree atrioventricular (AV) block and to compare with control subjects with normal ventricular conduction (CSNVC) METHODS: A total of one-fifty subjects were chosen (50 patients with LBBP, 50 patients with RVSP and 50 CSNVC). The indication for pacemaker implantation was symptomatic high degree AV block. Baseline clinical and electrocardiogram (ECG) parameters like QRS duration (QRSD), QRS axis and f QRS-T angle and Ejection Fraction (EF) were assessed. f QRS-T angle was measured as the difference between the computerised mean frontal QRS and T wave axes in the limb leads. If the difference between the QRS axis and T-wave axis exceeds 180°, then the resultant QRS-T angle would be calculated as 360° minus the absolute angle to obtain a value between 0° and 180°. Baseline, immediate post procedural and 6 month follow up (f/u) ECGs and EF were chosen for the analysis.

RESULTS

Patients who underwent LBBP had significantly shorter paced QRSD than patients who had undergone RVSP (112 ± 12 ms vs 146 ± 13 ms; 95 % confidence interval (CI): 43, -31; p<0.001). There was no significant difference in the QRSD before and after LBBP. The QRSD before and after pacing in RVSP was 111 ± 27 ms and 146 ± 13 ms; 95 % CI: 43, -28; p < 0.001. The QRSD in control patients with NVC was 82.94 ± 9.59 ms. RVSP was associated with wider f QRS-T angle when compared with LBBP (103 ± 53° vs 82 ± 43°; 95 % CI: 39, -1.0; p = 0.037). The baseline and immediate post procedure f QRS-T angle in LBBP was 70 ± 48° and 82 ± 43°; 95 % CI: 31, 5.3; p = 0.2. At 6 months f/u, the f QRS-T angle was 61 ± 43°; 95 % CI: 8.5, 35; p=0.002. The baseline and immediate post procedure f QRS-T angle in RVSP was 67 ± 51° and 103 ± 53°; 95 % CI: 54, -17; p < 0.001. At 6 months f/u, the f QRS-T angle in RVSP group was 87 ± 58°; 95 % CI: 2.6, 29; p = 0.020. The f QRS T angle in control patients with NVC was 24 ± 16°. When subgroup analysis was done the difference in the f QRS-T angle was significant between RVSP and LBBP groups only in patients who had wide QRS escape. The mean LVEF at 6-month follow-up in LBBP vs RVSP was 61 ± 3.7 % vs 57.1 ± 7.8 %; 95 % CI:1.48, 6.32, p = 0.002. In the RVSP group, three patients developed pacing induced cardiomyopathy (PIC) whereas no patients in the LBBP group developed PIC at 6-month follow-up; p=0.021. One patient with PIC had deterioration of functional status with new onset HF symptoms. The patient symptoms improved with medical therapy and needed no hospitalisation. The patient declined further interventions including upgradation to CRT or LBB pacing. No deaths or ventricular arrhythmias were observed during the study period.

CONCLUSION

LBBP is associated with narrower f QRS-T angle as compared to RVSP both at post implant period and at 6 month f/u period. These findings might be due to the more physiological depolarization and repolarization kinetics associated with LBBP. RVSP was associated with 6 % incidence of PIC. Hence wide f QRS-T angle might be a predictor of PIC.

Genetic architecture of spatial electrical biomarkers for cardiac arrhythmia and relationship with cardiovascular disease

The 3-dimensional spatial and 2-dimensional frontal QRS-T angles are measures derived from the vectorcardiogram. They are independent risk predictors for arrhythmia, but the underlying biology is unknown. Using multi-ancestry genome-wide association studies we identify 61 (58 previously unreported) loci for the spatial QRS-T angle (N = 118,780) and 11 for the frontal QRS-T angle (N = 159,715). Seven out of the 61 spatial QRS-T angle loci have not been reported for other electrocardiographic measures. Enrichments are observed in pathways related to cardiac and vascular development, muscle contraction, and hypertrophy. Pairwise genome-wide association studies with classical ECG traits identify shared genetic influences with PR interval and QRS duration. Phenome-wide scanning indicate associations with atrial fibrillation, atrioventricular block and arterial embolism and genetically determined QRS-T angle measures are associated with fascicular and bundle branch block (and also atrioventricular block for the frontal QRS-T angle). We identify potential biology involved in the QRS-T angle and their genetic relationships with cardiovascular traits and diseases, may inform future research and risk prediction.

Review of Processing Pathological Vectorcardiographic Records for the Detection of Heart Disease

Vectorcardiography (VCG) is another useful method that provides us with useful spatial information about the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common nowadays, mainly due to the well-established 12-lead ECG system. However, VCG leads can be derived from standard 12-lead ECG systems using mathematical transformations. These derived or directly measured VCG records have proven to be a useful tool for diagnosing various heart diseases such as myocardial infarction, ventricular hypertrophy, myocardial scars, long QT syndrome, etc., where standard ECG does not achieve reliable accuracy within automated detection. With the development of computer technology in recent years, vectorcardiography is beginning to come to the forefront again. In this review we highlight the analysis of VCG records within the extraction of functional parameters for the detection of heart disease. We focus on methods of processing VCG functionalities and their use in given pathologies. Improving or combining current or developing new advanced signal processing methods can contribute to better and earlier detection of heart disease. We also focus on the most commonly used methods to derive a VCG from 12-lead ECG.

Vectorcardiography as a prognostic tool in hypertrophic cardiomyopathy

BACKGROUND

Vectorcardiography (VCG) has demonstrated diagnostic value in the assessment of hypertrophic cardiomyopathy (HCM), however, determining its prognostic value over time has not yet been investigated. This study sought to assess the correlation of VCG parameters with the progression of HCM.

METHODS

A retrospective chart review of 119 pediatric patients with diagnosis of HCM at the University of Minnesota. Eighty-three cases were excluded because of age, presence of congenital heart disease, not meeting criteria for HCM or negative phenotype. Sample was divided into 2 groups based on the presence or not of cardiac events (ventricular tachycardia, cardiac arrest, ventricular assist device, heart transplant). Derived vectorcardiography from standard 12‑lead ECG was obtained for the first ECG and last available or prior to sentinel event.

RESULTS

Of the 36 cases that met inclusion criteria, 9 (25%) developed a sentinel event. The median age for the event group was 10.1 ± 7.5 years and for the non-event group was 8.7 ± 6.35 years. There was no significant difference in age or sex between the groups. The T wave vector magnitude value was significantly smaller in the event group than in the non-event group (0.302 ± 0.146 mV Vs. 0.561 ± 0.305 mV, p 0.002), with a hazard ratio of 0.651 (95% CI 0.463 to 0.915). No other parameter showed significant difference between the two groups.

CONCLUSIONS

The T wave vector magnitude may predict sentinel events in HCM. Prospective studies are necessary to evaluate the utility of the evolution of VCG parameters.

Gender- and age-related differences in distinct phenotypes of hypertrophic cardiomyopathy-associated mutation MYBPC3-E334K

The mutation MYBPC3-E334K is a culprit mutation of hypertrophic cardiomyopathy (HCM). The pathogenicity of MYBPC3-E334K is conflicting in ClinVar because of the limited segregation data and the relatively high frequency in gnomAD (0.03% overall, with 0.3% in East Asians and 0.8% in Japanese). The main aim is to clarify the clinical importance and phenotype-genotype correlations in subjects with or without MYBPC3-E334K alone. The prevalence of MYBPC3-E334K was sequenced in 1017 HCM unrelated probands. The clinical features, morphology phenotypes, and electrical phenotypes were further analyzed according to the phenotype and genotype status in families with single-mutation MYBPC3-E334K. Nine of 1017 (0.88%) unrelated HCM probands were detected harboring MYBPC3-E334K, and three of them harbored a second variant in sarcomere protein gene. Family study and co-segregation analyses indicated that patients with single-mutation MYBPC3-E334K showed autosomal dominant mode of inheritance with incomplete penetrance. The overall disease penetrance was 52.6%, and the disease penetrance was higher in males than in females (100% in men vs 25% in women, p = 0.003). The mean age at diagnosis of males was approximately 25 years younger than females (36.57 ± 18.65 vs 62.33 ± 12.10, p = 0.062). The variant MYBPC3-E334K was classified as a likely pathogenic variant, and a second sarcomere variant did not reveal obvious cumulative effects. The patients harboring single-mutation MYBPC3-E334K had incomplete penetrance, and males demonstrated higher penetrance and early onset HCM than females. A second sarcomere variant did not reveal obvious cumulative effects.

QRS-T angle in patients with Hypertrophic Cardiomyopathy - A comparison with Cardiac Magnetic Resonance Imaging

Objective: We sought to investigate the possible association of a wide QRS-T angle on the surface EKG and myocardial fibrosis on contrast-enhanced cardiovascular magnetic (CMR) imaging in patients with hypertrophic cardiomyopathy (HCM). Background: Risk stratification in HCM patients is challenging. Late gadolinium enhancement (LGE) visualizes myocardial fibrosis with unique spatial resolution and is a strong and independent prognosticator in these patients. The QRS-T angle from the surface EKG is a promising prognostic marker in various cardiac pathologies. Methods: 70 patients with HCM obtained a standardized digital 12-lead EKG for the calculation of the QRS-T angle and underwent comprehensive CMR imaging for visualization of fibrosis by LGE. Patients were divided into groups according to the absence or presence of fibrosis on CMR. Results: 43 of 70 patients with HCM showed LGE on CMR following contrast administration. HCM patients with LGE (fibrosis) had wider QRS-T angles as compared to the patient group without LGE (100±54 vs. 46±31; <0.001). A QRS-T angle of 90 degrees or more was a strong predictor (OR 32.84, CI 4.08-264.47; p <0.001) of HCM with LGE. Conclusion: There is a strong association of a wide QRS-T angle and myocardial fibrosis in patients with HCM.

Quantitative T-wave morphology assessment from surface ECG is linked with cardiac events risk in genotype-positive KCNH2 mutation carriers with normal QTc values

INTRODUCTION

Long QT syndrome (LQTS) mutation carriers have elevated the risk of cardiac events even in the absence of QTc prolongation; however, mutation penetrance in patients with normal QTc may be reflected in abnormal T-wave shape, particularly in KCNH2 mutation carriers. We aimed to assess whether the magnitude of a three-dimensional T-wave vector (TwVM) will identify KCNH2-mutation carriers with normal QTc at risk for cardiac events.

METHODS

Adult LQT2 patients with QTc < 460 ms in men and <470 ms in women (n = 113, age 42 ± 16 years, 43% male) were compared with genotype-negative family members (n = 1007). The TwVM was calculated using T-wave amplitudes in leads V6, II, and V2 as the square root of (TV6²  + TII²  + (0.5*TV2)² ). Cox regression analysis adjusted for gender and time-dependent beta-blocker use was performed to assess cardiac event (CE) risk, defined as syncope, aborted cardiac arrest, implantable cardioverter-defibrillator therapy, or sudden death.

RESULTS

Dichotomized by median of 0.30 mV, lower TwVM was associated with elevated CE risk compared to those with high TwVM (HR = 2.95, 95% CI, 1.25-6.98, P = .014) and also remained significant after including sex and time-dependent beta-blocker usage in the Cox regression analysis (HR = 2.64, 95% CI, 1.64-4.24, P < .001). However, these associations were found only in women but not in men who had low event rates.

CONCLUSION

T-wave morphology quantified as repolarization vector magnitude using T-wave amplitudes retrieved from standard 12-lead electrocardiogram predicts cardiac events risk in LQT2 women and appears useful for risk stratification of KCNH2-mutation carriers without QTc prolongation.

Integration of 12-Lead Electrocardiograms Into Preparticipation Screenings to Prevent Sudden Cardiac Death in High School Athletes

INTRODUCTION

Sudden cardiac arrest continues to be the leading cause of death in young athletes despite preparticipation sports screening (PPS). The devastating loss of children to sudden cardiac arrest has led communities to demand more comprehensive heart screenings. The purpose of this study was to evaluate a community youth heart screening program in Minnesota.

METHOD

A retrospective chart review of 840 participants aged 14 to 18 years from August 2015 through March 2017 was conducted.

RESULTS

Referrals were made for two abnormal electrocardiography results, 12 abnormal echocardiography results, and 59 elevated blood pressure readings. Cross-tabulations showed one participant with an abnormal electrocardiogram and six participants with abnormal echocardiograms who had no other abnormal findings at the screening. Findings were not statistically significant.

DISCUSSION

It was clinically significant that six participants were found to have potentially lethal electrical or structural heart abnormalities who would have otherwise have remained unidentified with the standard preparticipation sports screening guidelines.

Cardiomyopathy in the pediatric patients

Pediatric cardiomyopathies are a group of myocardial diseases with complex taxonomies. Cardiomyopathy can occur in children at any age, and it is a common cause of heart failure and heart transplantation in children. The incidence of pediatric cardiomyopathy is increasing with time. They may be associated with variable comorbidities, which are most often arrhythmia, heart failure, and sudden death. Medical imaging technologies, including echocardiography, cardiac magnetic resonance, and nuclear cardiology, are helpful in reaching a diagnosis of cardiomyopathy. Nevertheless, endomyocardial biopsy is the final diagnostic method of diagnosis. Patients warrant surgical operations, such as palliative operations, bridging operations, ventricular septal maneuvers, and heart transplantation, if pharmaceutical therapies are ineffective. Individual therapeutic regimens due to pediatric characteristics, genetic factors, and pathogenesis may improve the effects of treatment and patients' survival.

Clinical Application of the QRS-T Angle for the Prediction of Ventricular Arrhythmias in Patients with the Fontan Palliation

Fontan palliation patients are at risk for ventricular arrhythmias post-operatively. This study aimed to evaluate whether differences in the spatial QRS-T angle can reliably predict ventricular arrhythmias in patients who had undergone Fontan palliation. A total of 117 patients who had the Fontan palliation and post-Fontan catheterization were included. Ventricular arrhythmias were identified in nine patients. Measurements of ECG parameters including QRS vector magnitude, QRS duration, corrected QT interval, and spatial peaks QRS-T angles were performed, and compared between those with and without ventricular arrhythmias. The only ECG parameter to distinguish those with versus those without VA was the SPQRS-T angle (p < 0.001), which at a cut-off value of 102.9° gave sensitivity, specificity, positive and negative predictive values of 100.0, 57.0, 17.6 and 100.0%, respectively. Only the spatial peaks QRS-T angle differentiated those with and without ventricular arrhythmia development with a univariate HR 1.237 (95% CI 1.021-1.500) and a multivariate HR of 1.032 (1.009-1.056) when catheter measured parameters were taken into account. In Fontan patients, the spatial peaks QRS-T angle is a significant independent predictor of ventricular arrhythmias. Clinical usefulness of this parameter remains to be seen and should be tested prospectively.

Non-invasive electrocardiographic predictors of atrial arrhythmias in patients with the Fontan palliation

BACKGROUND

Fontan palliation patients are at risk for atrial arrhythmias post-operatively. This study aimed to evaluate whether differences in depolarization vector magnitude or spatial P-R angle can reliably predict atrial arrhythmias in patients who had undergone Fontan palliation.

METHODS

A total of 115 patients who had Fontan palliation and post-Fontan catheterization were included. Atrial arrhythmias were identified in 14 patients. Measurements of ECG parameters including QRS vector magnitude, P-R duration, spatial QRS-T angle and spatial P-R angle were performed, and compared between those with and without atrial arrhythmias.

RESULTS

Only the QRSvm independently differentiated those with and without atrial arrhythmias with multivariate HR of 0.743 (95% CI 0.581 to 0.951).

CONCLUSION

In Fontan patients, the QRSvm was the only significant independent predictor of atrial arrhythmias.

ECG-derived spatial QRS-T angle is associated with ICD implantation, mortality and heart failure admissions in patients with LV systolic dysfunction

Background

Increased spatial QRS-T angle has been shown to predict appropriate implantable cardioverter defibrilIator (ICD) therapy in patients with left ventricular systolic dysfunction (LVSD). We performed a retrospective cohort study in patients with left ventricular ejection fraction (LVEF) 31–40% to assess the relationship between the spatial QRS-T angle and other advanced ECG (A-ECG) as well as echocardiographic metadata, with all-cause mortality or ICD implantation for secondary prevention.

Methods

534 patients ≤75 years of age with LVEF 31–40% were identified through an echocardiography reporting database. Digital 12-lead ECGs were retrospectively matched to 295 of these patients, for whom echocardiographic and A-ECG metadata were then generated. Data mining was applied to discover novel ECG and echocardiographic markers of risk. Machine learning was used to develop a model to predict possible outcomes.

Results

49 patients (17%) had events, defined as either mortality (n = 16) or ICD implantation for secondary prevention (n = 33). 72 parameters (58 A-ECG, 14 echocardiographic) were univariately different (p<0.05) in those with vs. without events. After adjustment for multiplicity, 24 A-ECG parameters and 3 echocardiographic parameters remained different (p<2x10^-3). These included the posterior-to-leftward QRS loop ratio from the derived vectorcardiographic horizontal plane (previously associated with pulmonary artery pressure, p = 2x10^-6); spatial mean QRS-T angle (134 vs. 112°, p = 1.6x10^-4); various repolarisation vectors; and a previously described 5-parameter A-ECG score for LVSD (p = 4x10^-6) that also correlated with echocardiographic global longitudinal strain (R² = - 0.51, P < 0.0001). A spatial QRS-T angle >110° had an adjusted HR of 3.4 (95% CI 1.6 to 7.4) for secondary ICD implantation or all-cause death and adjusted HR of 4.1 (95% CI 1.2 to 13.9) for future heart failure admission. There was a loss of complexity between A-ECG and echocardiographic variables with an increasing degree of disease.

Conclusion

Spatial QRS-T angle >110° was strongly associated with arrhythmic events and all-cause death. Deep analysis of global ECG and echocardiographic metadata revealed underlying relationships, which otherwise would not have been appreciated. Delivered at scale such techniques may prove useful in clinical decision making in the future.

Lower spatial QRS-T angle rules out sustained ventricular arrhythmias in children with hypertrophic cardiomyopathy

Introduction The spatial peaks QRS-T angle accurately distinguishes children with hypertrophic cardiomyopathy from their healthy counterparts. The spatial peaks QRS-T angle is also useful in risk stratification for ventricular arrhythmias. We hypothesised that the spatial peaks QRS-T angle would be useful for the prediction of ventricular arrhythmias in hypertrophic cardiomyopathy patients under 23 years of age.

METHODS

Corrected QT interval and spatial peaks QRS-T angles were retrospectively assessed in 133 paediatric hypertrophic cardiomyopathy patients (12.4±6.6 years) with versus without ventricular arrhythmias of 30 seconds or longer. Significance, positive/negative predictive values, and odds ratios were calculated based on receiver operating characteristic curve cut-off values.

RESULTS

In total, 10 patients with ventricular arrhythmias were identified. Although the corrected QT interval did not differentiate those with versus without ventricular arrhythmias, the spatial peaks QRS-T angle did (151.4±19.0 versus 116.8±42.6 degrees, respectively, p<0.001). At an optimal cut-off value (124.1 degrees), the positive and negative predictive values of the spatial peaks QRS-T angle were 15.4 and 100.0%, respectively, with an odds ratio of 25.9 (95% CI 1.5-452.2).

CONCLUSION

In children with hypertrophic cardiomyopathy, the spatial peaks QRS-T angle is associated with ventricular arrhythmia burden with high negative predictive value and odds ratio.

Atrioventricular depolarization differences identify coronary artery anomalies in Kawasaki disease

BACKGROUND

Kawasaki disease (KD) is the leading cause of acquired heart disease in children. Signal average electrocardiogram changes in patients during the acute phase of KD with coronary artery anomalies (CAA) include depolarization changes. We set out to determine if 12-lead-derived atrioventricular depolarization differences can identify CAA in patients with KD.

METHODS

A blinded, retrospective case-control study of patients with KD was performed. Deep Q waves, corrected QT-intervals (QTc), spatial QRS-T angles, T-wave vector magnitudes (RMS-T), and a novel parameter for assessment of atrioventricular depolarization difference (the spatial PR angle) and a two dimensional PR angle were assessed. Comparisons between groups were performed to test for significant differences.

RESULTS

One hundred one patients with KD were evaluated, with 68 having CAA (67.3%, mean age 3.6 ± 3.0 years, 82.6% male), and 32 without CAA (31.7%, mean age 2.7 ± 3.2 years, 70.4% male). The spatial PR angle significantly discriminated KD patients with CAA from those without, 59.7° ± 31.1° versus 41.6° ± 11.5° (p < .001). A spatial PR angle cutoff value of 56.9° gave positive/negative predictive values and odds ratios of 93.8%, 43.5%, and 11.5% (95% confidence interval (CI) 2.6-52.2). The two dimensional PR angle either below 7° or above 92° gave positive/negative predictive values and odds ratios of 100.0%, 38.8%, and 21.1% (95% CI 1.2-362.8). No other parameters significantly differentiated the groups.

CONCLUSION

Atrioventricular depolarization differences, measured by the spatial or two dimensional PR angle differentiate KD patients with CAA versus those without.

Repolarization Vector Magnitude Differentiates Kawasaki Disease from Normal Children

INTRODUCTION

Kawasaki disease (KD) is the leading cause of acquired heart disease in children. The 12-lead electrocardiogram (ECG) changes in patients during the acute phase of KD include flattened T waves and prolonged corrected QT intervals (QTc). We set out to determine the 12-lead ECG and vectorcardiography predictors for identification of patients with KD and which of these predictors would be clinically useful for early identification of those with coronary artery anomalies (CAA).

METHODS

A blinded, retrospective case-control study of patients with KD and age-matched controls was performed. Deep Q waves, QTc, spatial QRS-T angles, and T-wave vector magnitude (root mean square of the T wave, RMS-T) were assessed. Comparisons between groups were performed to test for significant differences.

RESULTS

Fifty patients with KD (mean age 3.1 ± 3.1 years, 26% female) were compared to 50 previously healthy control patients (mean age 3.8 ± 2.9 years, 44% female). Of the KD patients, 32 (64%) were diagnosed as incomplete KD and 28 (56%) of them had CAA. When compared to the control group, KD patients had abnormal Q waves (72% vs 44% P = 0.005), shorter QTc values (395.1 ± 24.7 ms vs 410.4 ± 34.7 ms, P = 0.013), and lower RMS-T (0.42 ± 0.02 mV vs 0.63 ± 0.03 mV P < 0.001), respectively. Incomplete KD was also discriminated from controls by the same parameters. No differences were noted between KD patients with versus without CAA.

CONCLUSION

The RMS-T differentiates complete and incomplete KD from controls. KD patients with CAA were not differentiated from those without CAA.

In Hypertrophic Cardiomyopathy, the Spatial Peaks QRS-T Angle Identifies Those With Sustained Ventricular Arrhythmias

BACKGROUND

The spatial peaks QRS-T (SPQRS-T) angle differentiates hypertrophic cardiomyopathy (HCM) patients from controls. Increased angle confers arrhythmia risk in other populations.

HYPOTHESIS

We predict that the SPQRS-T angle will identify HCM patients with sustained ventricular arrhythmias (VAs) and those with New York Heart Association class III/IV heart failure.

METHODS

Corrected QT interval, QRS duration, and SPQRS-T angle were assessed in HCM patients with VAs (>30 seconds) and those without VAs.

RESULTS

One hundred HCM patients (mean age, 32.7 ± 17.2 years) were assessed. Twenty patients had VAs. The corrected QT interval identified VA (P = 0.018) and at 460 ms gave positive and negative predictive values of 28.6% and 83.3%, respectively, and an odds ratio of 2.0 (95% confidence interval: 0.7-5.6). The SPQRS-T angle differentiated VA from no VA (P < 0.001) and at 124.1 degrees gave positive and negative predictive values and an odds ratio of 36.7%, 96.1%, and 14.2 (95% confidence interval: 3.1-65.6), respectively.

CONCLUSIONS

The SPQRS-T angle best differentiated patients with VAs.

Differentiating hypertrophic cardiomyopathy from athlete's heart: An electrocardiographic and echocardiographic approach

Differential diagnosis of hypertrophic cardiomyopathy (HCM) vs athlete's heart is challenging in individuals with mild-moderate left-ventricular hypertrophy. This study aimed to assess ECG and echocardiographic parameters proposed for the differential diagnosis of HCM. The study included 75 men in three groups: control (n=30), "gray zone" athletes with interventricular septum (IVS) measuring 13-15mm (n=25) and HCM patients with IVS of 13-18mm (n=20). The most significant differences were found in relative septal thickness (RST), calculated as the ratio of 2 x IVS to left ventricle end-diastolic diameter (LV-EDD) (0.37, 0.51, 0.71, respectively; p<0.01) and in spatial QRS-T angle as visually estimated (9.8, 33.6, 66.2, respectively; p<0.01). The capacity for differential HCM diagnosis of each of the 5 criteria was assessed using the area under the curve (AUC), as follows: LV-EDD<54 (0.60), family history (0.61), T-wave inversion (TWI) (0.67), spatial QRS-T angle>45 (0.75) and RST>0.54 (0.92). Pearson correlation between spatial QRS-T angle>45 and TWI was 0.76 (p 0.01). The combination of spatial QRS-T angle>45 and RST>0.54 for diagnosis of HCM had an AUC of 0.79. The best diagnostic criteria for HCM was RST>0.54. The spatial QRS-T angle>45 did not add sensitivity if TWI was present. No additional improvement in differential diagnosis was obtained by combining parameters.