Time-Domain Heart Rate Variability in Coronary Artery Disease Patients Affected by Thyroid Dysfunction

Abstract

SummarySubclinical hypothyroidism and hyperthyroidism have been recognized as clinical entities with negative effects on the cardiovascular system. Moreover, the effect of treated thyroid dysfunction on parameters associated with the cardiovascular control system has been poorly investigated. In the present study we analyzed time-domain heart rate variability in coronary artery disease (CAD) patients with known thyroid diseases. Twenty-four hour ECG monitoring was performed in 344 patients with coronary artery disease (174 with thyroid dysfunction and 170 without thyroid dysfunction used as a control group), using a 3-channel tape recorder. Time domain parameters of heart rate variability (HRV) were defi nitely lower both in patients with subclinical hypothyroidism and subclinical hyperthyroidism than in the control group, with statistically signifi cant differences in SDNN, RMSSD, TINN, and mean RR for both subgroups. Furthermore, patients on L-thyroxine treatment and restored euthyroidism had generally higher HRV values than patients with subclinical hypothyroidism, nevertheless SDNN, RMSSD, SDNN index, TINN, and mean RR were signifi cantly lower when compared to those of the control group. Signifi cant differences in HRV were also found between hyperthyroid patients under treatment and control group subjects with respect to RMSSD, TINN, and mean RR values. In conclusion, patients with cardiac disease and known thyroid disease, even when the disease is in the subclinical range or despite treatment, should be regarded as patients at additional risk conveyed by thyroid hormone disturbances. (Int Heart J 2014; 55: 33-38) Key words: Hyperthyroidism, Hypothyroidism, Autonomic, Regulation, Cardiovascular risk T hyroid hormones perform a fundamental role in maintaining cardiovascular homeostasis, since they act both directly on the heart muscle and by modulating the autonomic nervous system. Typical clinical signs of hyperthyroidism such as increases in heart rate, cardiac output, systolic blood pressure, myocardial contractility, and basal metabolism and the presence of tremor suggest a hyperadrenergic state. This is possibly due to a greater sensitivity to catecholamines, since their plasmatic concentration in hyperthyroid patients is normal.1) It has been hypothesized that hyperthyroid patients could have alterations either in the number or in the affinity of adrenergic receptors.2) Hypothyroidism instead seems to evoke a hypoadrenergic state due to the presence of bradycardia, reduced cardiac output, and reduced basal metabolism. Intracellular catecholamine production from circulating lymphocytes has been found to be lower during short-term hypothyroidism in patients who have undergone thyroidectomy for differentiated thyroid carcinomas, as compared to the values found during hormone replacement therapy.3) Nevertheless, in contrast with the reduced adrenergic reactions at the cardiac, metabolic, and cellular levels, the plasmatic concentration of norepinephrine is increased in those patients.4) Through the ev...

Relationship between heart rate variability and subclinical thyroid disorders of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

“…Accordingly, previous studies with smaller sample sizes showed reduced variability in subjects with SCHyper compared to euthyroid ones (10,11,14,26). Goichot et al (11) detected lower values for SDNN in SCHyper subjects (N=12) compared to controls (N=32).…”

“…Goichot et al (11) detected lower values for SDNN in SCHyper subjects (N=12) compared to controls (N=32). Galetta et al (28) (SCHyper: N=30; controls: N= 30), Petretta et al (10) (SCHyper: N=30; controls: N= 20), and Falcone et al (14) (SCHyper: N=28; controls: N=170; all with coronary artery disease), besides lower SDNN, also detected reduced RMSSD and pNN50 values when comparing both groups. It is noteworthy that we did not find a marked cardiac parasympathetic withdrawal in SCHyper subjects; however, this group showed lower values in magnitude for parasympathetic indices in comparison to euthyroids.…”

“…Galetta et al (28), comparing 42 SCHypo subjects with 30 controls, found lower HF values in frequency domain analysis and reduced time domain indices. Falcone et al (14) evaluated 55 SCHyper subjects compared to 170 euthyroids and observed lower SDNN and RMSSD.…”

Cardiac autonomic function and vascular profile in subclinical hypothyroidism: Increased beat-to-beat QT variability

“…HF is a marker of vagal efferent signal that is modulated by ventilation. [ 34 ] HRV parameters were lower in cases as compared to controls in both time and frequency domains. HRV measures fluctuations in the autonomic inputs to the heart.…”

Oscillating blood pressure therapeutic target in type 2 diabetes patients with hypertension

“…Although there are evidence suggesting that strong reduction of BP does not reduce the rate of a composite outcome of fatal and nonfatal major cardiovascular events in type 2 diabetes patients, it is important to consider that most of these evidence were drawn from studies presenting some confounding factors such as the presence of previous CVD and events and the increase in cardiovascular outcomes found with excessive lowering of BP appeared at a level of BP <110 mmHg, a quite outlier values used for the development of recommendations and very rarely seen in patients with hypertension taking conventional treatment (9). On the other hand, despite the fact that some randomized controlled trials suggest that excessive reduction of BP is associated with an increase in cardiovascular mortality (10,11), there is still little evidence that this mortality excess is due to BP lowering. The recent findings of the study by Adamsson Eryd et al support this idea and relaunch the discussion on the J-shaped phenomenon of BP in type 2 diabetes patients (12).…”