The role of QRS complex prolongation in predicting severe toxicity in single-xenobiotic overdose

Figures & data

Figure 1. Flow diagram for patients included in the study.

Table 1. The demographics of patients in the study cohort who met inclusion criteria.

	Diphenhydramine		Bupropion		Amitriptyline		Nortriptyline		Quetiapine		Cocaine
	Prolonged QRS	Normal QRS	Prolonged QRS	Normal QRS	Prolonged QRS	Normal QRS	Prolonged QRS	Normal QRS	Prolonged QRS	Normal QRS	Prolonged QRS	Normal QRS
Total cases	75	1,504	39	951	66	431	20	38	26	926	19	560
Age (years)
Median	17	17	19	19	42	31	23.5	36.5	34	31	40	41
Interquartile range	14.75 − 27.25	15–29	15 − 31.5	16–32	17–54	17–46	15.75 − 42.75	19.5 − 49.75	23.5 − 46.5	18 − 46	32.5 − 47	30 − 51
Range	13–69	13–86	14–62	13–78	13–81	13–81	13–61	15–64	14–72	13 − 87	16 − 60	14 − 89
Sex
Female	41 (54.7%)	964 (64.1%)	26 (66.7%)	627 (65.9%)	46 (69.7%)	298 (69.1%)	14 (70.0%)	25 (65.8%)	20 (76.9%)	497 (53.7%)	5 (26.3%)	133 (23.8%)
Male	32 (42.7%)	525 (34.9%)	13 (33.3%)	313 (32.9%)	20 (30.3%)	132 (30.6%)	6 (30.0%)	13 (34.2%)	6 (23.1%)	423 (45.7%)	14 (73.7%)	425 (75.9%)
Transgender	2 (2.7%)	14 (0.9%)	0	9 (0.9%)	0	1 (0.2%)	0	0	0	4 (0.4%)	0	0
Unknown	0	1	0	2	0	0	0	0	0	2	0	2
Self-Harm Attempt
Yes	65 (86.7%)	1259 (83.7%)	36 (92.3%)	826 (86.9%)	58 (87.9%)	215 (49.9%)	19 (95.0%)	9 (23.7%)	22 (84.6%)	847 (91.5%)	1 (5.3%)	21 (3.8%)
No	8 (10.7%)	179 (11.9%)	1 (2.6%)	83 (8.7%)	2 (3.0%)	33 (7.7%)	1 (5.0%)	3 (7.9%)	3 (11.5%)	51 (5.5%)	18 (94.7%)	505 (90.2%)
Unknown	2	66	2	42	6	183	0	26	1	28	0	34

Figure 2. Odds ratios for clinical outcomes in patients with prolonged QRS complex compared to a normal QRS complex duration. Columns with no bar and an asterisk (*) signify an odds ratio where the 95% confidence interval did not show a significant difference in outcomes between patients with a prolonged compared to normal QRS complex duration. The error bars display the 95% confidence interval for each odds ratio, which may also be seen in Tables 2–5.

Table 2. Statistical analyses for patients with normal and prolonged QRS complex durations for developing seizures.

	Seizures/total cases with a prolonged QRS	Seizures/total cases with a normal QRS	Odds ratio of a seizure with a prolonged QRS compared to a normal QRS (95% CI)	Positive predictive value of a prolonged QRS for a seizure (95% CI)	Negative predictive value of a normal QRS for a seizure (95% CI)
Diphenhydramine	23/75 (30.7%)	173/1504 (11.5%)	3.4 (2.0 − 5.7)	30.7% (21.7 − 41.4%)	88.5% (88.0 − 89.0%)
Bupropion	24/39 (61.5%)	358/951 (37.6%)	2.7 (1.4 − 5.1)	61.5% (46.0 − 75.1%)	62.4% (61.7 − 63.0%)
Amitriptyline	16/66 (24.2%)	30/431 (7.0%)	4.3 (2.2 − 8.4)	24.3% (16.6 − 34.0%)	93.0% (91.5 − 94.3%)
Nortriptyline	9/20 (45.0%)	7/38 (18.4%)	3.6 (1.1 − 12.1)	45.0% (29.6 − 61.4%)	81.6% (71.2 − 88.8%)
Quetiapine	4/26 (15.4%)	34/926 (3.7%)	4.8 (1.6 − 14.6)	15.4% (6.2 − 33.4%)	96.3% (95.9 − 96.7%)
Cocaine	6/19 (31.6%)	34/560 (6.1%)	7.1 (2.6 − 20.0)	31.6% (15.6 − 53.5%)	93.9% (93.1 − 94.6%)

CI: confidence interval.

Table 3. Statistical analyses for patients with normal and prolonged QRS complex durations for developing ventricular dysrhythmias.

	Ventricular dysrhythmias/total cases with a prolonged QRS	Ventricular dysrhythmias/total cases with a normal QRS	Odds ratio of ventricular dysrhythmias with a prolonged QRS compared to normal QRS (95% CI)	Positive predictive value of a prolonged QRS for ventricular dysrhythmias (95% CI)	Negative predictive value of a normal QRS for ventricular dysrhythmias (95% CI)
Diphenhydramine	12/75 (16.0%)	9/1504 (0.6%)	31.6 (12.9 − 77.8)	16.0% (10.9 − 22.9%)	99.4% (99.0 − 99.6%)
Bupropion	2/39 (5.1%)	6/951 (0.6%)	8.5 (1.7 − 43.6)	5.1% (1.5 − 15.8%)	99.4% (99.1 − 99.6%)
Amitriptyline	12/66 (18.2%)	5/431 (1.2%)	18.9 (6.4 − 55.8)	18.2% (13.0 − 24.8%)	98.8% (97.6 − 99.4%)
Nortriptyline	2/20 (10.0%)	0/38 (0.0%)	Infinity (Incalculable)	10.0% (7.1 − 14.0%)	100.0% (90.8 − 100.0%)
Quetiapine	1/26 (3.9%)	2/926 (0.2%)	18.5 (1.6 − 210.6)	3.9% (0.8 − 17.2%)	99.8% (99.5 − 99.9%)
Cocaine	4/19 (21.1%)	11/560 (2.0%)	13.3 (3.8 − 46.6)	21.1% (9.1 − 41.5%)	98.0% (97.4 − 98.6%)

CI: confidence interval.

Table 4. Statistical analyses for patients with normal and prolonged QRS complex durations for developing metabolic acidosis.

	Metabolic acidosis/total cases with a prolonged QRS	Metabolic acidosis/total cases with a normal QRS	Odds ratio of a metabolic acidosis with a prolonged QRS compared to a normal QRS (95% CI)	Positive predictive value of a prolonged QRS for a metabolic acidosis (95% CI)	Negative predictive value of a normal QRS for a metabolic acidosis (95% CI)
Diphenhydramine	14/75 (18.7%)	24/1504 (1.6%)	14.1 (7.0 − 28.7)	18.7% (12.4 − 27.1%)	98.4% (98.0 − 98.7%)
Bupropion	5/39 (12.8%)	23/951 (2.4%)	5.9 (2.1 − 16.6)	12.8% (5.9 − 25.8%)	97.6% (97.1 − 98.0%)
Amitriptyline	7/66 (10.6%)	12/431 (2.8%)	4.1 (1.6 − 10.9)	10.6% (5.9 − 18.3%)	97.2% (96.1 − 98.0%)
Nortriptyline	1/20 (5.0%)	0/38 (0.0%)	Infinity (Incalculable)	5.0% (3.5 − 7.1%)	100.0% (90.8 − 100.0%)
Quetiapine	0/26 (0.0%)	11/926 (1.2%)	0 (0 - Undefined)	0.0% (0.0 − 100.0%)	98.8% (98.8 − 98.8%)
Cocaine	5/19 (21.1%)	36/560 (6.4%)	5.2 (1.8 − 15.2)	26.3% (11.9 − 48.5%)	93.6% (92.8 − 94.2%)

CI: confidence interval.

Table 5. Statistical analyses for patients with normal and prolonged QRS interval durations for deaths.

	Deaths/total cases with a prolonged QRS	Deaths/total cases with a normal QRS	Odds ratio of death with a prolonged QRS compared to a normal QRS (95% CI)	Positive predictive value of a prolonged QRS for death (95% CI)	Negative predictive value of a normal QRS for death (95% CI)
Diphenhydramine	5/75 (6.7%)	8/1504 (0.5%)	13.4 (4.3 − 41.9)	6.7% (3.3 − 12.9%)	99.5% (99.2 − 99.7%)
Bupropion	4/39 (10.3%)	3/951 (0.3%)	36.1 (7.8 − 167.5)	10.3% (5.3 − 19.0%)	99.7% (99.3 − 99.9%)
Amitriptyline	4/66 (6.1%)	1/430 (0.2%)	27.7 (3.1 − 252.2)	6.1% (3.8 − 9.6%)	99.8% (98.7 − 100.0%)
Nortriptyline	1/20 (5.0%)	0/38 (0.0%)	Infinity (Incalculable)	5.0% (3.5 − 7.1%)	100.0% (90.8 − 100.0%)
Quetiapine	0/26 (0.0%)	6/926 (0.7%)	0 (0 - Undefined)	0.0% (0.0 − 100.0%)	99.4% (99.4 − 99.4%)
Cocaine	2/19 (10.5%)	11/560 (2.0%)	5.9 (1.2 − 28.6)	10.5% (2.9 − 31.4%)	98.0% (97.5 − 98.4%

CI: confidence interval.

Data availability statement

Data for this manuscript was obtained by request from the American College of Medical Toxicology’s Toxicology Investigators Consortium: https://www.acmt.net/toxic/