Figure 1. Partial linear correlation of serum potassium versus ECG parameters while controlling for ionized calcium and bicarbonate on limited data set (n = 96).

Figure 2. Partial linear correlation of serum potassium versus ECG parameters while controlling for ionized calcium and bicarbonate on complete data set (n = 476).

Figure 3. ROC curves of T/R ratio in V4, PR and QRS using the complete data set (n = 476). The blue line shows the performance of ECG parameter. The green line is for reference.

Table 1. Demographics, electrocardiogram (ECG) characteristics, and mean serum electrolytes.

Table 1. Demographics, electrocardiogram (ECG) characteristics, and mean serum electrolytes.

CharacteristicValue (%)Age, years Mean ± SD46 ± 15Gender Male57Female39Race (Ethnicity) Hispanic89 (92.70)Asian3 (3.13)Black4 (4.17)ECG Characteristics Normokalemia (K ≤ 5.3 mEq/L)10 (10.40)Hyperkalemia (K ≥ 5.3 mEq/L)86 (89.60)Patient Visits476Normokalemia (K ≤ 5.3 mEq/L)50 (10.50)Hyperkalemia (K ≥ 5.3 mEq/L)426 (89.50)Mean Serum Electrolytes ± SD Potassium6.20 ± 0.77Ionized Calcium0.97 ± 0.15Sodium135.90 ± 7.56Chloride107 ± 5.28Bicarbonate20.30 ± 4.32Glucose110.30 ± 49.00Blood Urea Nitrogen104.80 ± 29.40Creatinine12.40 ± 7.69

Table 2. Partial linear correlations of T/R ratio by lead, PR, and QRS vs. serum potassium.

Table 2. Partial linear correlations of T/R ratio by lead, PR, and QRS vs. serum potassium.

Sample Size (N)ECG CharacteristicCorrelation
CoefficientAdjusted R Squarep-Value (2-Tailed) T/R Ratio Lead n = 95V20.230.040.04n = 94V30.170.020.02n = 95V40.170.020.02n = 92PR0.260.060.06n = 95QRS0.350.120.12 T/R Ratio Lead n = 466V20.210.04<0.01n = 472V30.170.03<0.01n = 465V40.170.03<0.01n = 457PR0.290.06<0.01n = 469QRS0.310.09<0.01

Table 3. Receiver operating characteristic (ROC) analysis for T/R ratio by lead, PR, and QRS.

Table 3. Receiver operating characteristic (ROC) analysis for T/R ratio by lead, PR, and QRS.

Sample Size (N)ECG Test VariableCutoff Threshold
(Optimal)Sensitivity
(Optimal)Specificity
(Optimal)Positive Predictive Value
(Optimal)Negative Predictive Value
(Optimal)Area
Under ROC Curve
(95% CI)p-Value T/R Ratio Lead n = 95V2≥0.75
(≥0.48)0.68
(0.82)0.80
(0.70)0.97
(0.96)0.23
(0.33)0.80
(0.65–0.94)<0.01n = 94V3≥0.75
(≥0.43)0.67
(0.91)0.60
(0.60)0.93
(0.95)0.18
(0.43)0.73
(0.55–0.92)0.02n = 95V4≥0.75
(≥0.37)0.43
(0.73)0.78
(0.67)0.95
(0.96)0.13
(0.21)0.73
(0.54–0.92)0.02n = 92PR≥200 ms
(≥144 ms)0.08
(0.86)1.00
(0.56)1.00
(0.95)0.11
(0.29)0.69
(0.48–0.90)0.07n = 95QRS≥120 ms
(≥82 ms)0.02
(0.81)1.00
(0.60)1.00
(0.95)0.11
(0.27)0.71
(0.52–0.90)0.03 T/R Ratio Lead n = 466V2≥0.75
(≥0.57)0.67
(0.76)0.58
(0.52)0.93
(0.93)0.17
(0.20)0.68
(0.61–0.76)<0.01n = 472V3≥0.75
(≥0.58)0.64
(0.75)0.60
(0.56)0.93
(0.94)0.16
(0.22)0.68
(0.59–0.76)<0.01n = 465V4≥0.75
(≥0.51)0.39
(0.55)0.77
(0.70)0.94
(0.94)0.12
(0.15)0.62
(0.53–0.71)<0.01n = 457PR≥200 ms
(≥144)0.08
(0.85)0.94
(0.35)0.91
(0.92)0.10
(0.21)0.55
(0.46–0.65)0.23n = 469QRS≥120 ms
(≥92)0.11
(0.49)1.00
(0.77)1.00
(0.95)0.10
(0.15)0.67
(0.59–0.74)<0.01