Clinical research
Cardiac magnetic resonance
Does subclinical hypothyroidism affect cardiac pump performance?: Evidence from a magnetic resonance imaging study

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Objectives

We sought to assess the effects of subclinical hypothyroidism (SHT) on the cardiac volumes and function.

Background

The cardiovascular system is one of the principal targets of thyroid hormones. Subclinical hypothyroidism is a common disorder that may represent “early” thyroid failure.

Methods

Thyroid profile was evaluated in 30 females with SHT and 20 matched control subjects. Left ventricular end-diastolic volume (EDV) and end-systolic volume (ESV), stroke volume (SV), cardiac index (CI), and systemic vascular resistance (SVR) were calculated by cardiac magnetic resonance (CMR). Regional greatest systolic lengthening (E1) and greatest systolic shortening (E2) were calculated by tagging CMR.

Results

EDV was lower in SHT than in controls (64.3 ± 8.7 ml/m2vs. 81.4 ± 11.3 ml/m2, p < 0.001), as well as SVR (38.9 ± 7.5 ml/m2vs. 52.5 ± 6.1 ml/m2, p < 0.001) and CI (2.6 ± 0.5 l/[min·m2] vs. 3.7 ± 0.4 l/[min·m2], p < 0.001). Systemic vascular resistance was higher in SHT (12.5 ± 2.5 mm Hg·min/[l·m2] vs. 8.6 ± 1.1 mm Hg·min/[l·m2], p = 0.003). The E1 was higher in controls than in SHT at the basal (p = 0.007), equatorial (p = 0.05), and apical (p = 0.008) levels, as well as E2 at the equatorial (p = 0.001) and apical (p = 0.001) levels. All parameters normalized after replacement therapy. A negative correlation between TSH and EDV (p < 0.001), SV (p < 0.001), CI (p < 0.001), and E1 at the apical level (p < 0.001) and a positive correlation between TSH and SVR (p < 0.001) and E2 at the apical level (p < 0.001) were found.

Conclusions

Subclinical hypothyroidism significantly decreased cardiac preload, whereas it increased afterload with a consequent reduction in SV and cardiac output. Replacement therapy fully normalized the hemodynamic alterations.

Abbreviations and acronyms

CI
cardiac index
CMR
cardiac magnetic resonance
DWT
diastolic wall thickness
E1
greatest systolic lengthening
E2
greatest systolic shortening
EDV
end-diastolic volume
ESV
end-systolic volume
FT3
free tri-iodothyronine
FT4
free thyroxine
LV
left ventricular
SHT
subclinical hypothyroidism
SV
stroke volume
SVR
systemic vascular resistance
TSH
thyroid-stimulating hormone

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