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EP.037
What is wrong with this heart?

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What’s wrong with this heart?

Dr Jennifer Hares,  Dr Nitin Arora

1. ST5, West Midlands Deanery, 2. Consultant, Heart of England NHS Trust

 

Introduction

Cardiomyopathies are defined as diseases of the myocardium associated with cardiac dysfunction.

In 1995 the World Health Organisation and the International Society and Federation of Cardiology classified cardiomyopathies as dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy (1).

DCM is a progressive disease of the heart muscle characterized by dilatation and impaired contraction of the left ventricle or both ventricles. It has many causes including idiopathic, familial/genetic, viral and/or immune, alcoholic/toxic, or associated with recognized cardiovascular disease. (1)

Although peripartum cardiomyopathy (PPCM) closely resembles Dilated Cardiomyopathy, it is now accepted that PPCM is a distinct entity.

The clinical course of PPCM has features that are unusual in other forms of cardiomyopathy. It has a highly variable and, sometimes, rapid progression to end-stage heart failure and, as in this case presentation, can often occur within a few days. The other specific feature to PPCM is the potential for spontaneous and complete recovery of ventricular function (2).

Significance of Case

Peripartum cardiomyopathy is an idiopathic cardiomyopathy presenting with heart failure secondary to left ventricular (LV) systolic dysfunction towards the end of pregnancy or in the months following delivery, where no other cause of HF is found.

It is a diagnosis of exclusion.

The LV may not be dilated but the ejection fraction (EF) is nearly always reduced below 45% (4).

In this case presentation there may be another cause for the development of cardiomyopathy – a profoundly hypothyroid state.

Reduced T3 production is known to have a negative impact on cardiac function, however Tang et al (3) proposed, using an animal model, that a low thyroid state causes cardiac atrophy with chamber dilatation, impaired myocardial blood flow, loss of arterioles, and severe systolic dysfunction. A dramatic reduction in myocardial arterioles results in impaired myocardial blood flow.

Patient Description

34-year-old lady who was 31 weeks pregnant, gravida 8 para 4.

She had a past medical history of;

•Thalassaemia trait
•Axonal motor sensory neuropathy
•Guillain-Barré syndrome– 2 years ago
•Hypothyroid – stopped medication 2013
•Anxiety
•Learning difficulties

Her current obstetric history included;

•Late booker
•Body Mass Index= 48
•Hypothyroid – for which she was given thyroxine
•Gestational diabetes
•Polyhydramnios
•Estimated foetal weight on 5th – 10th centile

She was seen in antenatal clinic by a consultant obstetrician and booked to attend labour suite the following day for steroids and a variable rate insulin infusion.

Presented the following day with shortness of breath,

On examination, hypoxic, tachypnoeic and tachycardic

CTPA: Consolidation bilaterally; no PE

Accepted for ICU with working diagnosis of Community Acquired Pneumonia

 

Management on ITU

CPAP with 10cm H2O

Dexamethasone given, with plan for LSCS if deteriorates

Overnight: Patient tiring. NIV started

BP rising so given stat dose of oral Labetolol

Next Morning

NIV iPAP +14 ePAP +10

FiO2 0.65

RR 27

HR 105

BP 140/89 mmHg

Lower Segment Caesarean Section performed

•Stayed on NIV (100% O2) until induction
•Prepped & draped pre-induction
•Desaturated to ~60% on induction
•Baby had O2sats of <50% & needed intubating
•Baby extubated D2, CPAP for 4 days & is fine
•Transferred back to ITU ventilated & on Adrenaline & Noradrenaline

Laboratory results

•TSH: 25
•T3/T4: undetectable
•D2: Started on IV Liothryonine (T3)
•On D5, started absorbing, and NG T4 also started
•By D7, TSH <10, and off vasopressors; D11: extubated
 

Formal ECHO report

•Severely dilated & hypokinetic LV with overall severely impaired systolic function, with an ejection fraction (EF) between 25 - 30% by visual assessment.
•Moderate functional central jet of mitral regurgitation is present.
•Mild generalised pericardial effusion. No tamponade
 

Discussion/ Conclusion

Biologically active T3 influences several important genes encoding for structural and functional proteins of the myocardium. These include contractile proteins within the thick filament of the myocyte and effects on the sarcoplasmic reticulum controlling calcium cycling.   These effects on the cardiac myocyte result in thyroid function being intimately associated with cardiac function. Thyroid hormone also has extra nuclear nongenomic actions on ion pumps and enzymes with rapid, direct effects on the cardiac myocyte and on the systemic vasculature.  Together, the genomic and nongenomic effects of T3 act together to regulate cardiac function.

Not only does hypothyroidism plays an important role in the progression of IDCM but it can also orchestrate cellular changes within the myocardium which resemble the pathological changes in IDCM 

 

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