Thyroid and Cardiovascular Disease: A Focused Review on the Impact of Hyperthyroidism in Heart Failure

The association between thyroid hormones and cardiovascular conditions has been well studied, specifically, the effects of hypothyroidism on cardiomyopathy, and hyperthyroidism with arrhythmias. Nonetheless, an explicit correlation between hyperthyroidism and cardiomyopathy has yet to be established. Medical databases MEDLINE and PubMed were accessed and queried as primary sources for data acquisition. Search criteria consisted of “hyperthyroidism”, “heart failure”, and “thyroid and cardiovascular system”, which allowed the retrieval of relevant and recent works. From these sources, a consensus was developed and employed to yield an updated review of the etiology of heart failure in the setting of hyperthyroidism. It is rare for patients with hyperthyroidism to remain in a chronic hyperthyroid state, making it difficult to analyze subsequent long-term effects on the cardiovascular system. Related to heart failure, some studies have demonstrated no change in ejection fraction, while others have shown an acute change along with diastolic dysfunction, with or without an underlying rhythm abnormality. Further investigation is warranted to elucidate the mechanism driving such cardiac dysfunction, and whether it is due to vascular changes, tachyarrhythmias, or myocyte remodeling and fibrosis. The intent of this review article is to improve our understanding of how a hyperthyroid state affects cardiovascular function. An enhanced understanding of the effects on cardiovascular physiology will afford physicians the ability to provide more comprehensive care in consideration of both endocrine and cardiovascular pathologies.

Asymptomatic adult intrapericardial diaphragmatic hernia detected on cardiac SPECT CT

An 83-year-old man underwent exercise stress test with single photon emission computed tomography (SPECT) myocardial perfusion imaging for new electrocardiogram (EKG) changes. The stress EKG did not show any significant changes. Myocardial perfusion imaging with SPECT demonstrated an inferior wall defect and extracardiac uptake of nuclear tracer. Simultaneous cardiac computed tomography performed for attenuation correction showed presence of intrapericardial hepatic tissue in an anterior diaphragmatic hernia. The herniated tissue was noted to influence the perfusion image and cause the defect. To date, this is a unique finding based on review of literature.

Diarrhea-An uncommon presentation of tertiary adrenal insufficiency following heart transplantation

Diarrhea following organ transplantation is usually associated with infection and immunosuppression therapy. We describe two patients with diarrhea following orthotopic heart transplantation due to tertiary adrenal insufficiency.

Abstract 297: Paroxysmal And Sustained Atrial Fibrillation In A New Large Animal Model Of Nonischemic Heart Failure

Introduction: Atrial fibrillation is common in heart failure (HF). Understanding of the mechanisms of atrial fibrillation (AF) is limited by the paucity of large animal AF models, especially in the failing heart. We developed a large animal model of nonischemic heart failure (HF) in dogs by combined aortic insufficiency and aortic constriction and observed that a number of HF dogs developed paroxysmal AF on holter monitor. Here we characterize the spontaneously-occurring pAF in these HF dogs and perform electrophysiologic (EP) assessment of atrial refractoriness and AF inducibility along with echocardiographic imaging of left ventricle (LV) and left atrium (LA).

Methods: HF was induced in dogs by aortic insufficiency and aortic constriction, and serial echocardiography (for LV fractional shortening (FS) and LA size) and Holter monitoring was performed. In control and HF dogs, EP study of atrial refractory period (AERP) and AF inducibility (duration and atrial cycle length (CL)) was performed.

Results: By Holter monitoring, paroxysmal AF was noted in 5 dogs with episodes ranging from 15 to 94 beats long (mean of 49±27 beats, n=12). In EP studies, control dogs (N=3) exhibited AERP of 176±8 ms. Burst pacing resulted in AF of very brief duration (mean 32±24 sec) and a mean AF CL of 138±6 ms. LV FS averaged 37% and LA size averaged 4.3 cm2. HF dogs (N=5) exhibited RAERP of 150±8 (p=0.05 vs control). Two of these dogs had sustained AF with ventricular response up to 230 bpm on Holter monitor. In the other 3 HF dogs, burst pacing induced AF with a mean duration of 232±185 sec (at times with conversion to atrial flutter) and with a mean AF CL = 110±4 ms (p=0.002 vs control). Echo data showed LVFS averaged 30% and LA area of 14.9 cm2 (p=0.05 vs control).

Conclusion: Thus we have developed a novel large animal model of HF that exhibits paroxysmal and sustained AF. This model will provide an opportunity for the study of underlying AF mechanisms, the progression of remodeling in HF hearts leading to AF, and the assessment of human-scale interventions to better treat and prevent this arrhythmia.

Neointimal hyperplasia and vasoreactivity are controlled by genetic elements on rat chromosome 3

Neointimal hyperplasia (NIH) can lead to restenosis after clinical vascular interventions. NIH results from complex and poorly understood interactions between signaling cascades in the extracellular matrix and the disrupted endothelium, which lead to vessel occlusion. Quantitative trait loci (QTLs) were reported previously on rat chromosomes 3 and 6 through linkage analysis of postinjury NIH in midiliac arterial sections. In the current study, substitution mapping validated the RNO3 NIH QTL but not the RNO6 NIH QTL. The SHR.BN3 congenic strain had a 3-fold increase in the percentage of NIH compared with the parental spontaneously hypertensive rat strain. A double congenic study of RNO3+RNO6 NIH QTL segments suggested less than additive effects of these 2 genomic regions. To test the hypothesis that changes in vessel dynamics account for the differences in NIH formation, we performed vascular reactivity studies in the Brown Norway (BN), spontaneously hypertensive rat (SHR), SHR.BN3, and SHR.BN6 strains. De-endothelialized left common carotid artery rings of the SHR.BN3 showed an increased vascular responsiveness when treated with serotonin or prostaglandin F2(alpha), with significant differences in EC(50) and maximum effect (P<0.01) values compared with the spontaneously hypertensive rat parental strain. Because both vascular reactivity and percentage of NIH formation in the SHR.BN3 strain are significantly higher than the SHR strain, we postulate that these traits may be associated and are controlled by genetic elements on RNO3. In summary, these results confirm that the RNO3 NIH QTL carries the gene(s) contributing to postinjury NIH formation.