To the best of our knowledge, this is the first study to report the effects of acromegaly, complication (HT and/or DM), as well as persistent uncontrolled active acromegaly after therapy on QT interval. Our results showed that both acromegaly and complication prolonged QT interval in subjects. More importantly, we found that there is positive interaction between acromegaly and complication, which means acromegaly with complication significant prolong QT interval compared with subjects with acromegaly and subjects with complication. In addition, QT interval in persistent uncontrolled active acromegaly at follow-up was significantly longer than the value at pre-treatment. Serum GH level and complication (HT and/or DM) have a significant positive relationship with prolonged QT interval.
In acromegaly, long-term persistent excess serum GH/IGF-1 contribute to cardiac overgrowth, resulting in arrhythmias and/or conduction disorders(3). In the past decades, previous studies have suggested prevalence and the severity of ventricular arrhythmias were significantly higher compared with controls by electrocardiogram and Holter studies in acromegaly(21, 22). For example, complex ventricular arrhythmias was detected in 48% of acromegalic patients compared with only 12% of controls with 24-h Holter ECG(21). Ventricular arrhythmias are clinically relevant, as it not only affects quality of life but also life threatening. QT intervals, reflecting the duration of ventricular repolarization, is an important period for the development of ventricular arrhythmias. QTc, correcting heart rate in QT intervals, has long been recognized as a marker of increased cardiovascular risk and provide important prognostic information in clinical practice(23). Only a few studies investigated the alteration of QTc in acromegaly and found prolonged QTc compare with healthy population with a relatively small sample size(12, 19, 24). In our study, 307 acromegalic patients and 303 patients with non-functional pituitary adenoma were included to study the difference of QTc between two group. As consistent with previous studies, our result further demonstrated that prolonged QT interval in acromegaly population compare with controls by large sample data.
In acromegaly, long-term persistent excess serum GH/IGF-1 contribute to overgrowth of interstitial fibrous tissue within the myocardium is thought to be the predominant factor responsible for cardiac rhythm abnormalities(12, 25, 26). It is well known that both HT and DM are frequent complication at the time of first diagnosis in acromegaly and also HT and DM are notoriously associated with the development of arrhythmias. Maffei et al. detected heart rate variability is reduced in acromegaly patients, especially with HT and/ or DM, compare to healthy populations(27). To avoid the effect of DM and HT on QT intervals, CAKIR et al. recruit the control group from individuals with similar comorbidities (DM, HT) to the acromegalic patients(19). In our study, all subjects were divided into four groups (acromegaly with complication, acromegaly without complication, controls with complication, and controls without complication) to investigate the effect of acromegaly and complication on QTc using factorial design two-way ANOVA. We found both acromegaly and complication significantly prolong QTc. Our results suggesting that both acromegaly and complication is an independent risk factor for ventricular arrhythmias. Notedly, we found that acromegalic patients with complication have significantly higher QTc than acromegalic patients without complication and controls with complication. This result suggested acromegalic patients with complication have a higher risk for ventricular arrhythmias.
Surgery, drug therapy, and radiotherapy are commonly used strategy in acromegalic patients to control serum GH/IGF-1 levels(13). Fatti et al have reported QTc significantly reduced in acromegalic patients with primary somatostatin analogues therapy(12). Recently, acromegalic patients with surgery was also found have statistically significant improvement QTc(19). These studies suggested effective therapy can decrease the risk of ventricular arrhythmias in acromegaly. It has been already known that long-term persistent serum excess GH/IGF-1 is one of the main factors of cardiac dysfunction in acromegaly(28–30). In our study, persistent uncontrolled active acromegalic patients after surgery and drug therapy were included. In these uncontrolled active acromegalic patients, serum GH and IGF-1 levels significantly decrease relative to pre-treatment, but not up to cure standard. Compare to pre-treatment, we found persistent uncontrolled serum excess GH/IGF-1 significantly increase the QTc. This result suggested the serum GH/IGF-1 levels in acromegaly patients should be strictly controlled, significantly reduce of serum GH/IGF-1 levels but not reach the normal level after therapy can not decrease the risk of ventricular arrhythmia.
In patients with acromegaly, serum GH and IGF-1 levels, age, course of disease, complication with hypertension and/or diabetes, and cardiovascular disease are the main determinants of mortality(31, 32). In the current study, we assess association of QTc with these clinical and echocardiographic variables. Previous studies have reported no relationship between GH/IGF-1 levels and QTc(12, 19, 24). However, we found significant positive relationship between GH level and QTc. No associate was detected in previous studies may be due to relatively small sample size in their research. More importantly, we also found complication with HT and/or DM are markedly related to QTc. This finding further suggested acromegalic patients with HT and/or DM have higher risk for ventricular arrhythmia than acromegalic patients without HT and/or DM. As for course of disease, similar to previous studies, no significant relationship with QTc was found in the present study(12, 19). There are some reasons including most patients could not provide the time at which the symptoms began because the discovery of the disease was due to change in appearance, systemic comorbidities or to local tumor effects(33). In addition, the time from tumorigenesis to the onset of symptoms does not provide an accurately assess the effect of on ventricular repolarization because different tumors secrete different hormones at different levels and individuals exhibit differences in hormone sensitivity.