Introduction:
The interstage mortality rate for hypoplastic left heart syndrome (HLHS) is high at 12%. Modalities to predict clinical decline would be useful in this high risk population. Due to cardiac conduction system anomalies in HLHS, electrocardiogram (ECG) monitoring of the ST segment is confounded. Our aim is to develop a monitor of ST variability that predicts deterioration despite the presence of an abnormal ST segment baseline.
Hypothesis:
Increased ST variability is associated with clinical deterioration in HLHS.
Methods:
A prospective, observational study was conducted at Texas Children’s Hospital using interstage recordings of 5 lead ECG. From January 2013 to January 2014, 25 subjects were admitted with HLHS; 21 had requisite ECG data for inclusion. In 11 subjects, there were 17 deterioration events, defined as rapid response team (RRT) activation. Events included 13 instances of respiratory failure with intubation and 4 instances of chest compressions. The control group included 10 subjects with no deterioration. An approach to quantify variability was developed where the ST segment vector was resolved using 3 orthogonal leads (II, V5, and aVF) and variability quantified with two metrics: 1) Displacement: distance between ST vector tips at 30 s intervals and 2) Component range: sum of ST vector tip movement in 3 dimensions over 10 min intervals. Comparison was made with the four hour window prior to RRT activation in the deterioration group against the four hour window prior to ICU discharge in the control group.
Results:
Four hours prior to clinical deterioration, increased ST variability was noted in both methods. For the 30 s displacement method, subjects with deterioration had a median value of 0.059 mm [IQR: 0.039 - 0.075] compared with 0.037 mm [IQR: 0.025 - 0.053] in the control group (p = 0.023). For the 10 min component range method, subjects with deterioration had a median value of 3.0 mm [IQR: 1.8 - 4.5] compared with 1.9 mm [IQR: 1.0 - 2.8] in the control group (p = 0.031).
Conclusions:
ST variability is increased in HLHS subjects prior to deterioration. Although conduction abnormalities limit the utility of ST monitoring in this population, quantification of ST variability may have a role in advanced systems to monitor clinical deterioration.
Outcomes of Patients With Hypoplastic Left Heart Syndrome Reaching Adulthood After Fontan Palliation
