Lay summary by Baldip Shergill
Edited by Crystal Han
This is a lay summary of the original research article by ICORD researchers Dr. Andrei Krassioukov and Shane Balthazaar and in collaboration with their colleagues in Denmark. Read the original article here.
What was the purpose of this study?
This study followed participants for six months, and was done as a follow-up to a previous study which looked at how often arrhythmias occurred in the first month following a spinal cord injury (SCI). Arrhythmias are a family of heart conditions that causes the heart to beat at an irregular pace (either faster or slower than normal). Note that an arrhythmia is not just a singular condition, but rather an umbrella term which covers multiple conditions that causes the heart to beat irregularly.
The study also compared the prevalence of arrhythmias between people with a cervical or thoracic SCI to determine if there were differences in the frequency of occurrence depending on the level of the injury.
How was the study done?
Participants were at least 18 years of age and had an SCI from the spinal levels of C1 to T12. A total of 55 participants were included in this study, of which 44 had cervical SCI and 11 had thoracic SCI. A cervical SCI ranges from C1-C8, or from the head to shoulders regions, and a thoracic SCI ranges from T1-T12, which extends from the shoulder blades down to the stomach. The sample size for the thoracic group was quite small compared to that of the cervical group.
Holter monitors, which can record heart rhythm and rate for 24 hours, were used in this study to measure heart rate and prevalence of arrhythmias.
What did the researchers find?
Immediately following SCI, participants who sustained cervical injuries had a lower average maximum heart rate compared to participants who sustained thoracic injuries. This lower average maximum heart rate can lead to events such as bradycardia, or cardiac arrest. Bradycardia occurs when the heart beats slower than normal, whereas cardiac arrest occurs when the heart stops beating completely. But, at around six months following the injury, no major differences were seen between participants with cervical or thoracic SCI. This suggests that improvements in average heart rate does occur over time, as the average maximum heart rate of participants with cervical SCI increased to meet the average maximum heart rate of the participants with thoracic SCI.
Supraventricular tachycardia (SVT), an abnormally fast heart rate, is one type of arrhythmia that can lead to heart failure. SVTs occurred more frequently for the cervical SCI group compared to the thoracic SCI group in week one and two. Over time, the amount of SVT events that occurred decreased.
The findings showed that the occurrence of cardiac arrhythmias, such as bradycardia or SVT are more common in the first month after an SCI, with results showing cardiac arrhythmias being more prominent for participants with a cervical SCi. However, at the six-month mark, there were no differences in the frequency of arrhythmias between the cervical and thoracic SCI participants. Overall, it appears that the heart’s function improves as time progresses following an SCI, and it could beneficial to receive care within the first six months following the injury, and especially for individuals with cervical SCI, as they presented with initially decreased average heart rate prior to the six-month mark.
Why is the study important for the SCI community?
The findings seem to suggest that receiving cardiac rehabilitation within the first six months following injury is more important for people with a cervical SCI, as they appear to face more challenges due to increased frequency of arrhythmias. But, after the first six months, the occurrence of cardiac arrhythmias appeared to level off between the participants in the cervical and thoracic SCI groups.