Diabetic Heart Disease

Despite advances in the detection and treatment of cardiovascular disorders, about one in four deaths in America are caused by heart disease annually. [1] But heart disease is only one of many chronic medical conditions adults experience. The American Heart Association cites heart disease as the cause of death in “at least 68 percent of people age 65 or older,” and there is an established link between cardiovascular disease and diabetes that suggests heart health has implications beyond the circulatory system. [2]

Left ventricular hypertrophy

A potential indicator of type 2 diabetes, hyperinsulinemia is a condition, often a result of insulin resistance, that involves excessive levels of insulin in the blood regardless of glucose levels. [3] Hyperinsulinemia can thicken the heart’s left ventricular wall over time. [4] As a result, the overdeveloped muscle becomes less efficient at pumping oxygenated blood to the body’s tissues and organs.

The heart in this illustration highlights the chamber of the left lower ventricle, which features heart wall that is thickened as a result of hyperinsulinemia. This thickening makes the muscled too stiff to contract forcefully.

Myocardial lipotoxicity

Both type 1 and type 2 diabetes may cause fatty acid deposits to accumulate within the myocardium — the heart’s muscle fibers. These deposits in turn can impair cell signaling and even cause myocardial cells to die. [5]

The illustration here exhibits fatty deposits along the left exterior chambers of the myocardium, or heart muscle.

Interstitial collagen deposits

Diabetes can promote excessive amounts of collagen to build up around cardiac blood vessels and within the heart muscle itself. These fibrous deposits cause the tissue to become rigid and stiff, making it difficult for the heart to contract forcefully since it no longer has the elastic stretch it needs to expand and then retighten. [6]

The heart illustration features a pulmonary artery clogged with collagen, blocking blood flow and making the vessel too rigid to expand and accommodate more circulation.

Diastolic dysfunction

In a normal heart, the ventricles relax and fill with blood during diastole, which is the “quiet period” of the heartbeat cycle. However, in some people with diabetes, the ventricles never fully relax — a condition called diastolic dysfunction [7]— which reduces the capacity of the ventricles’ reservoir to refill with blood. This means that when the heart goes into systole, or  “the active period,” there isn’t enough blood pumped out of the heart and into the body, resulting in reduced circulation and, eventually, pulmonary congestion [8], wherein fluid accumulates in the lungs and limits or prevents gas exchange.

In the illustration the lower right ventricle of the heart is mid contraction and unable to fill completely with de-oxygentated blood. Because the ventricle does not fill completely, not enough blood is circulated onward during an atrial kick, resulting in a weak blood flow.

SOURCES

[1] “Heart Disease Facts,” Centers for Disease Control (2015), accessed April 6, 2017, https://www.cdc.gov/heartdisease/facts.htm

[2] “Cardiovascular Disease and Diabetes,” American Heart Association (2016), accessed March 28, 2017, http://www.heart.org/HEARTORG/Conditions/More/Diabetes/WhyDiabetesMatters/Cardiovascular-Disease-Diabetes_UCM_313865_Article.jsp#.WNk0naK1tPY

[3] “Hyperinsulinemia: Is It Diabetes?,” Mayo Clinic (2014), accessed March 29, 2017, http://www.mayoclinic.org/diseases-conditions/type-2-diabetes/expert-answers/hyperinsulinemia/faq-20058488

[4] Guanghong Jia, Vincent G. DeMarco, and James R. Sowers, “Insulin resistance and hyperinsulinaemia in diabetic cardiomyopathy,” Nature Reviews Endocrinology 12, no. 3 (2016), accessed August 4, 2017,

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4753054/

[5] Adam R. Wende and E. Dale Abel, “Lipotoxicity in the Heart,” Biochimica et Biophysica Acta 1801, no. 3, (2010), accessed April 4, 2017, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2823976/

[6] Loek van Heerebeek, Nazha Hamdani, M. Louis Handoko, Ines Falcao-Pires, et al, “Diastolic Stiffness of the Failing Diabetic Heart: Importance of Fibrosis, Advanced Glycation End Products, and Myocyte Resting Tension,” Circulation 117, no. 1 (2008), accessed August 4, 2017, http://circ.ahajournals.org/content/117/1/43.full

[7] “Diastolic Dysfunction and Diastolic Heart Failure,” Summit Medical Group, accessed August 4, 2017, http://www.summitmedicalgroup.com/library/adult_health/car_diastolic_dysfunction/

[8] “Diastolic Dysfunction,” Texas Heart Institute, accessed August 4, 2017, http://www.texasheart.org/HIC/Topics/Cond/ddisfunc.cfm


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