The Institute of cardiology, National Hospital of Sri Lanka, Colombo has been the leading tertiary care center, which entertain the referrals from all around the country as well as direct admissions. The cardiac electrophysiology service has started in year 2005 and since then for more than a decade, this institute was the main service supplier. This study has bridged the gap of evidence deficiency in CRT implantation including follow up consequences by evaluating the demographics and clinical parameters and analyzing the efficacy of CRT as a heart failure treatment modality.
According to the international literature, the mean age of CRT implantation in USA was 65.4 (+/-10.8) years, UK 63.9 ± 10.7 years and a meta-analysis done in Korea has shown a range from 58 to 72 years [1, 2, 12]. These age ranges are higher compared to the mean age of the study population which was 52.82+/-11.66 years. This shows the impact of age in selecting patients for CRT implantation as well as life expectancy differences in Sri Lanka compared to other developed countries with higher health care facilities and higher life expectancy.
According to census data in National Statistics in Sri Lanka the gender distribution of the country is male 48.4% and female 51.6% [3]. This might have been a factor for this study population to have a female predominance (56%). In contrast, most of the studies done in developed countries has shown a male predominance such as in USA 72%, UK 68%, France 81.2% [1, 2, 13]. The beneficial effects of CRT implantation in the study population of females has shown better values than male (female = 78.57%, male = 45.45%). This trend has been seen in a study which was conducted in USA in 2015 [14].
The prevalence of associated comorbidities of heart failure in the CRT implanted population in Sri Lanka has shown that hypertension and diabetic mellitus as the predominant conditions. A study conducted in Canada in year 2010 has shown similar distribution of comorbidities in heart failure patients who had undergone resynchronization therapy, which highlights a prevalence of hypertension (52%) and diabetic (16%) [15].
A meta-analysis on cardiac resynchronization in patients with symptomatic heart failure and a study which was conducted by Mark A. Ileret et al have shown that ischemic cardiomyopathy as the leading etiological factor for heart failure (58% and 65% respectively) [16, 17]. But in this study, most of the patients had idiopathic dilated cardiomyopathy as the major contributing factor for heart failure. This might not have affected the outcome of data, as it was shown by meta-analysis done in USA in 2013, that CRT has similar benefits in both ischemic and non ischemic groups [18].
There was a significant improvement in NYHA functional class with CRT implantation in this study population and almost a similar functional class improvements have been observed in two separate studies done in USA in 2007, 2008 (59% improvement) and UK in 2022 (52% improvement) [2, 19]. In contrast to subgroup analysis of NYHA functional class in this study, Alan J. Banka et al. has conducted a study done in Minnesota during 2012 which shows that, improvement of clinical status, LV function and size of NYHA functional class I/II CRT patients were good or better than those in NYHA functional class III/ IV [20]. A similar trend has been observed in a meta-analysis which was done by Nawaf S. Al-Majed et al. in 2011[11].
QRS width has been considered as a surrogate marker to measure the efficacy of CRT implantation improvement. The functional class improvement of NYHA has been 88.4% for the subgroup of QRS width improved. Studies done in Canada and Korea have shown the similar beneficial effect of QRS improvement with regard to CRT efficacy [21, 12]. Sander G. Molhoek et. al. in Netherlands has observed that baseline QRS width is not a good predictor to determine the efficacy of CRT [22].
Several international studies have shown a pre CRT EF of 20% – 30%, whereas our study has a mean pre CRT EF of 30.91+/-10.28%. This might be resulted by less stringent adherence of guideline recommendation to CRT implantation [7, 13, 23]. Most of the meta-analysis done in western part of the world during early 21st century proves a significant improvement in EF following CRT [7, 9, 24].
A significant improvement of LV EDD has been noted in a study done by William T. Abraham et al. in UK which has shown a median LV EDD improvement with CRT implantation of -3.5mm in patients with mean of pre CRT LV EDD as 70 ± 10mm comparable to the similar findings in our study which has been noted as 10mm median LV EDD improvement in patients with 59.8+/-10.59 mm mean pre CRT LVEDD [9].
The rate of complications have been low in this study compared to other international systematic reviews and meta-analysis done during 2003 to 2007 [7, 11, 16], but this may be due to the low population number.
Limitations :
The cardiac electrophysiology was a new entity in cardiology field of Sri Lanka which was introduced in year 2005 with the limited resources. It was gradually expanded over past years gaining new experiences. With these circumstances, there was a limitation of data which had led to reduced total number of patients who were eligible for the study as well as less availability of medical records as some of them were discarded and missing. In addition, In addition the number of implants were low particularly in the early years as CRT was a relatively new procedure and as most patients were dependent on free devices through the National Health system, the availability of devices were also restricted. Mortality could not be assessed as planned due to difficulty of following up patients over past 15 years.