Coronary Artery Disease Case File

Coronary Artery Disease Case File

Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

CASE 16

A 59-year-old man complains of tight chest pressure and shortness of breath after lifting several boxes in his garage approximately 2 h ago. He perceives that his heart is skipping beats. His medical history is significant for hypertension and cigarette smoking. On examination, his heart rate is 55 beats/min and regular, and his lungs are clear to auscultation. An electrocardiogram shows bradycardia with an increased PR interval and ST-segment elevation in multiple leads including the anterior leads, V1 and V2.

⯈ What is the most likely diagnosis?

⯈ What anatomical structures are most likely affected?

ANSWER TO CASE 16:

Coronary Artery Disease

Summary: A 59-year-old hypertensive male smoker has a 2-h history of tight chest pressure, shortness of breath, and palpitations after exertion. His heart rate is 55 beats/min and regular. The electrocardiogram (ECG) shows bradycardia, first-degree heart block, and ST-segment elevation in leads V1 and V2.

• Most likely diagnosis: Myocardial infarction

• Anatomical structures likely affected: Right coronary artery and left anterior descending artery

CLINICAL CORRELATION

This patient’s 2-h history of worsening chest pain, dyspnea, and palpitations after physical exertion is classic for a myocardial infarction. The pain of angina due to the myocardial ischemia is typically deep, visceral, and squeezing in nature, like an “elephant stepping on the chest.” It frequently radiates to the neck or left arm. This patient’s risk factors include hypertension and tobacco use. The ECG (ST-segment elevation) is highly suspicious for myocardial infarction. Leads V1 and V2 are used to evaluate the anterior portion of the heart, which is supplied by the left anterior descending artery. Bradycardia and first-degree heart block (increased PR interval) indicate right coronary artery disease.

APPROACH TO:

Coronary Artery Circulation

OBJECTIVES

1. Be able to describe the course and areas of the heart supplied by the right and

left coronary arteries, respectively

2. Be able to describe the venous drainage of the heart

3. Be able to describe the arterial supply and venous drainage of the pericardial sac

DEFINITIONS

ANGINA: Chest pain classically described as pressure or squeezing indicative of coronary artery insufficiency and cardiac ischemia

ISCHEMIA: Inadequate blood supply and oxygen delivery to tissue

PALPITATIONS: Pulsations of the heart perceptible by a patient that are usually irregular and increased in force

BRADYCARDIA: Heart rate no higher than 60 beats/min

DISCUSSION

The heart receives its arterial blood supply from the first branches of the ascending aorta, the right and left coronary arteries. The right and left arteries arise from the aorta at the aortic sinuses, the pockets formed by the right and left cusps of the aortic valve, respectively. Each artery will supply portions of the atria and ventricles.

The right coronary artery (RCA) arises at the right aortic sinus and courses in the coronary (AV) groove between the right atrium and ventricle. At the level of the right auricular appendage, it gives off the SA nodal branch, which ascends to the junction of the SVC with the right atrium, where the SA node is located. As it reaches the inferior margin of the heart in the coronary groove, it will usually give off a right marginal branch that supplies the right ventricle along the inferior border. The RCA then curves around the inferior margin of the heart in the coronary groove onto the inferior and posterior surfaces of the heart, passing somewhat to the left toward the junction with the posterior interventricular groove, also called the crux of the heart. At the crux, the AV nodal branch passes deep into the interatrial septum to supply the AV node. The RCA divides into a larger posterior interventricular artery, which descends in the groove or sulcus of the same name. It passes toward but typically does not reach the apex of the heart. It supplies the right and left ventricles and posterior portions of the interventricular septum. A small branch continues to the left side of the heart to supply portions of the left atrium and ventricle and will anastomose with the circumflex branch of the left coronary artery (LCA) (see Figures 16-1 and 16-2).

Figure 16-1. Anterior view of the heart: 1 = aortic arch, 2 = superior vena cava, 3 = pulmonary trunk, 4 = right auricle, 5 = right atrium, 6 = coronary sulcus and vessels, 7 = epicardial fat, 8 = inferior vena cava, 9 = right ventricle, 10 = ligamentum arteriosum, 11 = left auricle, 12 = left ventricle, 13 = anterior interventricular sulcus and vessels. (Reproduced, with permission, from the University of Texas Health Science Center Houston Medical School.)

Figure 16-2. Posterior view of the heart: 1 = aortic arch, 2 = pulmonary arteries, 3 = pulmonary veins, 4 = left atrium, 5 = superior vena cava, 6 = right atrium, 7 = inferior vena cava, 8 = coronary sinus, 9 = posterior interventricular sulcus and vessels, 10 = left ventricle. (Reproduced, with permission, from the University of Texas Health Science Center Houston Medical School.)

The LCA arises from the left aortic sinus and quickly bifurcates into an anterior interventricular and circumflex arteries. The anterior interventricular or left anterior descending (LAD) artery descends toward the apex of the heart in the anterior interventricular groove, where it curves around the apex onto the diaphragmatic surface of the heart to anastomose with the posterior (descending) interventricular branch of the RCA. The anterior interventricular artery supplies the anterior portion of the right and left ventricles and anterior two-thirds of the interventricular septum and therefore is the chief blood supply to the AV and the right and left bundles of the heart’s conducting system. The other, smaller, branch of the LCA is the circumflex branch, which travels in the coronary groove toward the left margin of the heart, at which point it typically gives off a left marginal branch that supplies the left heart border portion of the left ventricle. The circumflex artery curves around the left heart border to anastomose with the RCA at the posterior aspects of the left atrium and ventricle. The pattern of arterial blood supply at this point is often described as a balanced blood supply because the RCA and LCA supply approximately equal amounts to the heart. In approximately 15 percent of the population, the LCA will supply a larger proportion than the RCA.

The majority of venous blood will enter the right atrium through the coronary sinus, which lies in the coronary groove on the posterior surface of the heart. Its internal opening is adjacent to the opening of the IVC. Great, middle, and small cardiac veins and several smaller named veins drain into the coronary sinus. A variable number of small anterior cardiac veins drain directly into the right atrium. The smallest cardiac veins drain small amounts of blood from the myocardial capillary plexus directly into the atria and ventricles.

The heart’s pericardial sac receives its arterial blood supply primarily from the pericardiacophrenic artery (a branch of the internal thoracic artery) that accompanies the phrenic nerve. Small amounts of arterial blood are also provided by branches of the musculophrenic, superior phrenic, bronchial, and esophageal arteries. Pericardiacophrenic veins drain blood to the internal thoracic or brachiocephalic veins.

COMPREHENSION QUESTIONS

16.1 As a cardiologist, you are concerned about blockage of the artery to the SA node in a patient. This artery typically arises from which of the following?

A. RCA

B. Right marginal artery

C. Posterior interventricular artery

D. Anterior interventricular artery

E. Circumflex artery

16.2 In a balanced coronary artery pattern, the blood supply to the majority of the interventricular septum is derived from which of the following?

A. RCA

B. Internal mammary artery

C. Posterior interventricular artery

D. Anterior interventricular artery

E. Circumflex artery

16.3 As a cardiologist, you are concerned about blockage of the artery to the AV node in a patient. This artery typically arises from which of the following?

A. RCA

B. Right marginal artery

C. Posterior interventricular artery

D. Anterior interventricular artery

E. Circumflex artery

16.4 A 56-year-old man is complaining of chest pain that radiates to the jaw and left arm. A thallium stress test shows decreased perfusion to the heart that overlies the diaphragm. Which of the following coronary arteries is most likely to be blocked?

A. Left anterior descending

B. Right coronary

C. Left main artery

D. Left circumflex

ANSWERS

16.1 A. The SA node is typically supplied by the RCA.

16.2 D. Usually, the anterior two-thirds of the interventricular septum is supplied by the AV artery, and the right and left bundle branches of the conduction system are generally supplied by the anterior interventricular artery.

16.3 A. The AV node is also supplied by the RCA.

16.4 B. The inferior portion of the heart is supplied by the right coronary artery.

ANATOMY PEARLS

⯈ In a balanced coronary circulation as described above, the conduction system nodes of the heart (SA and AV nodes) are typically supplied by the RCA.

⯈ In a balanced coronary circulation, the anastomoses between branches of the RCA and LCA occur at the posterior coronary and posterior interventricular grooves.

⯈ Most cardiac veins drain into the coronary sinus, which opens into the right atrium adjacent to the opening of the IVC.

References

Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:96−97. 

Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:144−148, 154−157. 

Netter FH. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 215−216.

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