QTc interval, and autonomic and somatic nerve function in diabetic neuropathy

Deterioration of cardiac autonomic function over a period of one year in relation to cardiovascular and somatic neuropathy complications in type 2 diabetes mellitus

AIMS

Progression of cardiac autonomic dysfunction (CADF) in relation to severity of diabetic autonomic neuropathy is well documented. But its progression while coexisting with somatic neuropathy (PNP) and cardiovascular disease (CVD) is less described. We monitored CADF over a period of one year in relation to PNP and CVD in patients with type 2 diabetes mellitus.

METHODS

Cardiac autonomic function was assessed in 104 type 2 diabetics. Based on complications study subjects were divided into four subgroups: Group A (No complications); Group B (with CVD); Group C (with PNP); Group D (with CVD and PNP). The parameters measured were: Expiratory:Inspiratory ratio (E:I ratio) and standard deviation of all the N-N intervals (SDNN). These parameters were measured at the baseline and at follow-up. Data analysis was done by employing suitable statistical tests.

RESULTS

In Group B: SDNN declined (p<0.001); E:I ratio did not change. In Group C: E:I ratio declined (p<0.01); SDNN did not change. In Group D: SDNN and E:I ratio declined significantly (p<0.001).

CONCLUSION

CADF coexisting with PNP and CVD deteriorates with time. E:I ratio and SDNN are suitable markers in monitoring CADF coexisting with PNP and CVD respectively in type 2 diabetes mellitus.

Diabetes as a risk factor for cardiac conduction defects: a review

Diabetes mellitus (DM) is a major risk factor for cardiovascular disease and mortality with increasing prevalence in the ageing population. Coronary artery disease is the major cardiovascular abnormality in DM patients. Cardiomyopathy and left ventricular hypertrophy are two other known associated cardiovascular abnormalities. There are a few non-randomized studies reporting increased prevalence of cardiac conduction abnormalities, such as right bundle branch block (RBBB), bifascicular block and high degree atrioventricular (AV)-block but not left bundle branch block (LBBB), in DM patients. Most clinicians are not aware of this association, and it is rarely mentioned in the published reviews about cardiovascular abnormalities in this population. The cause of cardiac conduction abnormalities in DM patients is not known. If autonomic neuropathy or DM-associated cardiovascular disease plays a role, it remains unknown. The goal of this manuscript is to review the current literature about the risk of conduction abnormalities in DM patients. For this study, Medline, Google and published books were searched and reviewed for any references that matched cardiac conduction abnormalities, AV-block, BBB for bundle branch block, LBBB, RBBB, bifascicular block, autonomic neuropathy and DM.

Shortened QT interval: a distinctive feature of the dysautonomia of chronic fatigue syndrome

PURPOSE

Because autonomic nervous functioning is frequently abnormal in chronic fatigue syndrome (CFS), we examined whether the corrected QT interval (QTc) in CFS differs from QTc in other populations.

METHODS

The QTc was calculated at the end of 10 minutes of recumbence and the end of 10 minutes of head-up tilt. In a pilot study, groups of 15 subjects, CFS, and controls, matched for age and sex, were investigated. In a second phase of the study, the QTc was measured in larger groups of CFS (n = 30) and control patients (n = 96) not matched for demographic features.

RESULTS

In the pilot study, the average supine QTc in CFS was 0.371 +/- 0.02 seconds and QTc on tilt, 0.385 +/- 0.02 seconds, significantly shorter than in controls (P = .0002 and .0003, respectively). Results of phase II confirmed this data.

CONCLUSIONS

Relative short QTc intervals are features of the CFS-related dysautonomia. The significance of this finding is discussed.

Abnormalities of rate-corrected QT intervals in Parkinson's disease-a comparison with multiple system atrophy and progressive supranuclear palsy

A number of patients with Parkinson's disease (PD) and multiple system atrophy (MSA), in whom sudden death does occur occasionally, have QT or rate-corrected QT (QTc) interval prolongation on electrocardiogram (ECG). Although these QT or QTc interval abnormalities are likely related to autonomic dysfunction, the pathophysiology remains unknown. The aim of this study was to compare the degree of QTc interval prolongation among akinetic-rigid syndromes, namely PD and related disorders, and to evaluate the relationship between QTc prolongation and severity of autonomic dysfunction. Thirty-four patients with PD, 22 with MSA, 11 with progressive supranuclear palsy (PSP) and 30 healthy controls underwent standard autonomic function tests, and electrocardiography variables (RR, QT and QTc intervals) were measured by an ECG recorder with an automated analyzer. The relationship between QTc interval and cardiovascular reflex tests were also analyzed. Orthostatic hypotension and decreased heart rate in response to respiratory stimuli were prominent in MSA, while these were relatively mild in PD. Unlike the RR and QT intervals, the QTc interval significantly differed among all groups (p<0.01). The QTc interval was significantly prolonged in PD (409+/-17 ms; p<0.001) and MSA (404+/-14 ms; p<0.05) compared with healthy controls (394+/-19 ms). Neither autonomic dysfunction nor QTc interval prolongation was evident in PSP. QTc intervals and cardiovascular reflexes did not correlate, except for Valsalva ratio. The QTc interval was obviously prolonged in PD patients to an extent that could not be accounted for simply by autonomic dysfunction levels. MSA patients showed slightly prolonged QTc intervals in spite of marked cardiovascular autonomic dysfunction. Abnormalities of the QTc may reflect the degeneration of cardioselective sympathetic and parasympathetic neurons that cannot be fully captured by cardiovascular autonomic function tests.