Prediction of Left Ventricular Mass Index Using Electrocardiography in Essential Hypertension – A Multiple Linear Regression Model

Figures & data

Table 1 Non-ECG Continuous Variables Tested for Inclusion in the Predictive Model for Left Ventricular Mass Index (LVMI)

Non-ECG Continuous Variables	Mean±Std. Deviation	Pearson Correlation	P value
Age (years)	56.38±11.83	0.03	0.76
Weight (kg)	68.24±12.22	−0.22	0.01
Height (cm)	161.17±8.49	0.05	0.57
Body Surface Area (m^2)	1.72±0.16	−0.20	0.02
Pulse rate (beats/minute)	81.09±13.96	−0.08	0.37
Systolic BP (mm of Hg)	162.68±21.99	0.28	0.001
Diastolic BP (mm of Hg)	92.96±12.13	0.26	0.001
Mean BP (mm of Hg)	116.20±12.78	0.32	<0.001
Duration of hypertension (years)	6.02±5.39	−0.001	0.99

Note: A two-tailed P value<0.05 was considered statistically significant.

Table 2 Non-ECG Categorical Variables Tested for Inclusion in the Predictive Model for Left Ventricular Mass Index (LVMI)

Non-ECG Categorical Variables	Frequency/Percent	Pearson Correlation	P value
Gender (Men/Percentage)	97/66%	0.04	0.67
Ischemic heart disease (Present/Percentage)	47/38%	0.35	<0.001
Diabetes (Present/Percentage)	45/30.6%	0.04	0.64
Dyslipidemia (Present/Percentage)	24/16.3%	−0.11	0.17

Note: A two-tailed P value<0.05 was considered statistically significant.

Table 3 ECG Continuous Variables Tested for Inclusion in the Predictive Model for Left Ventricular Mass Index (LVMI)

Sum of Deflections	Mean±Std. Deviation	Pearson Correlation	P value
(i) Limb leads (LL)	27.24±9.41	0.60	<0.001
(ii) Augmented limb leads (ALL)	22.16±7.06	0.64	<0.001
(iii) Precordial leads (PL)	110.70±34.87	0.51	<0.001
(iv) All twelve leads (ATL)	160.10±44.60	0.56	<0.001
(v) Sokolow Lyon criteria (SL)	25.54±10.58	0.49	<0.001
(vi) Cornell voltage criteria (CV)	17.93±8.06	0.53	<0.001

Note: A two-tailed P value<0.05 was considered statistically significant.

Table 4 Stepwise Forward Selection Method for Construction of Multiple Linear Regression Model Predictive of LVMI

Step	Variables Added	P value	VIF	R^2	Adj. R^2	Variables Removed
1	Augmented limb leads (ALL)	<0.001	1.00	0.408	0.404
2	Augmented limb leads (ALL)	<0.001	7.50	0.408	0.400	Limb leads (LL)
	Limb leads (LL)	0.880	7.50
3	Augmented limb leads (ALL)	<0.001	2.15	0.424	0.416
	All twelve leads (ATL)	0.043	2.15
4	Augmented limb leads (ALL)	<0.001	2.27	0.450	0.438	All twelve leads (ATL)
	All twelve leads (ATL)	0.340	2.51
	Cornell voltage criteria (CV)	0.010	1.77
5	Augmented limb leads (ALL)	<0.001	1.67	0.460	0.449	Precordial leads (PL)
	Cornell voltage criteria (CV)	0.040	1.86
	Precordial leads (PL)	0.060	1.76
6	Augmented limb leads (ALL)	<0.001	2.16	0.459	0.447	Sokolow Lyon criteria (SLC)
	Cornell voltage criteria (CV)	0.002	1.52
	Sokolow Lyon criteria (SLC)	0.073	1.64
7	Augmented limb leads (ALL)	<0.001	1.66	0.458	0.446
	Cornell voltage criteria (CV)	0.002	1.52
	Mean BP (mm of Hg)	0.083	1.14
8	Augmented limb leads (ALL)	<0.001	1.70	0.504	0.490
	Cornell voltage criteria (CV)	0.001	1.53
	Mean BP (mm of Hg)	0.072	1.14
	Ischemic heart disease (Present)	<0.001	1.04

Figure 1 Scatter plots of ECG variables against the dependent variable (LVMI). (A) Sum total of deflections in augmented limb leads (ALL) (R=0.64). (B) Sum of deflection of R wave in aVL and S wave in V3, Cornell Voltage(CV) (R=0.53).

Abbreviation: LVMI, left ventricular mass index.

Table 5 Best Fit Model for LVMI with Retained Significant Predictors

Predictor	Unstandardized Coefficient	Adj. R^2	P value
Aug. limb leads	1.704	0.404	<0.0001
Ischaemic Heart disease	15.406	0.448	<0.0001
Cornell Voltage	0.969	0.482	0.001
Mean blood pressure	0.295	0.490	0.072

Note: A two-tailed P value<0.05 was considered statistically significant.

Abbreviations: Adj. R², adjusted R square; Aug. limb leads, sum of deflections in augmented limb leads; Cornell Voltage, sum of deflections as in Cornell criteria; MBP, mean blood pressure; IHD, presence of ischemic heart disease.

Figure 2 (A) Histogram of standardised residuals indicating normal distribution. All residuals are lying within the limit of 3 SDs. (B) Scatter plot of standardised residuals against standard predicted values. The dots are uniformly distributed on either side of the horizontal line at the level of standardised residual=0. The plot shows homogeneity of variance at different standardised predicted values.

Figure 3 (A) Scatter plot of predicted against the observed values of LVMI in the hold-out validation method (R=0.69). (B) Scatter plot of predicted against the observed values of LVMI in the leave-one-out validation method (R=0.62).

Abbreviation: LVMI, left ventricular mass index.