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12: Cardiovascular Emergencies Cognitive Objectives (1 of 11) 4-3.1 Describe the structure and function of the cardiovascular system. 4-3.2 Describe the emergency medical care of the patient experiencing chest pain/discomfort. 4-3.3 List the indications for automated external defibrillation (AED). 4-3.4 List the contraindications for automated external defibrillation. 4-3.5 Define the role of EMT-B in the emergency cardiac care system. Cognitive Objectives (2 of 11) 4-3.6 Explain the impact of age and weight on defibrillation. 4-3.7 Discuss the position of comfort for patients with various cardiac emergencies. 4-3.8 Establish the relationship between airway management and the patient with cardiovascular compromise. 4-3.9 Predict the relationship between the patient experiencing cardiovascular compromise and basic life support. Cognitive Objectives (3 of 11) 4-3.10 Discuss the fundamentals of early defibrillation. 4-3.11 Explain the rationale for early defibrillation. 4-3.12 Explain that not all chest pain patients result in cardiac arrest and do not need to be attached to an automated external defibrillator. 4-3.13 Explain the importance of prehospital ACLS intervention if it is available. Cognitive Objectives (4 of 11) 4-3.14 Explain the importance of urgent transport to a facility with Advanced Cardiac Life Support if it is not available in the prehospital setting. 4-3.15 Discuss the various types of automated external defibrillators. 4-3.16 Differentiate between the fully automated and the semiautomated defibrillator. 4-3.17 Discuss the procedures that must be taken into consideration for standard operations of the various types of automated external defibrillators. Cognitive Objectives (5 of 11) 4-3.18 State the reasons for assuring that the patient is pulseless and apneic when using the automated external defibrillator. 4-3.19 Discuss the circumstances which may result in inappropriate shocks. 4-3.20 Explain the considerations for interruption of CPR when using the automated external defibrillator. 4-3.21 Discuss the advantages and disadvantages of automated external defibrillators. Cognitive Objectives (6 of 11) 4-3.22 Summarize the speed of operation of automated external defibrillation. 4-3.23 Discuss the use of remote defibrillation through adhesive pads. 4-3.24 Discuss the special considerations for rhythm monitoring. 4-3.25 List the steps in the operation of the automated external defibrillator. Cognitive Objectives (7 of 11) 4-3.26 Discuss the standard of care that should be used to provide care to a patient with persistent ventricular fibrillation and no available ACLS. 4-3.27 Discuss the standard of care that should be used to provide care to a patient with recurrent ventricular fibrillation and no available ACLS. 4-3.28 Differentiate between the single rescuer and multi-rescuer care with an automated external defibrillator. Cognitive Objectives (8 of 11) 4-3.29 Explain the reason for pulses not being checked between shocks with an automated external defibrillator. 4-3.30 Discuss the importance of coordinating ACLS trained providers with personnel using automated external defibrillators. 4-3.31 Discuss the importance of postresuscitation care. 4-3.32 List the components of postresuscitation care. Cognitive Objectives (9 of 11) 4-3.33 Explain the importance of frequent practice with the automated external defibrillator. 4-3.34 Discuss the need to complete the Automated Defibrillator: Operator’s Shift Checklist. 4-3.35 Discuss the role of the American Heart Association (AHA) in the use of automated external defibrillation. 4-3.36 Explain the role medical direction plays in the use of automated external defibrillation. Cognitive Objectives (10 of 11) 4-3.37 State the reasons why a case review should be completed following the use of the automated external defibrillator. 4-3.38 Discuss the components that should be included in a case review. 4-3.39 Discuss the goal of quality improvement in automated external defibrillation. 4-3.40 Recognize the need for medical direction of protocols to assist in the emergency medical care of the patient with chest pain. Cognitive Objectives (11 of 11) 4-3.41 List the indications for the use of nitroglycerin. 4-3.42 State the contraindications and side effects for the use of nitroglycerin. 4-3.43 Define the function of all controls on an automated external defibrillator, and describe event documentation and battery defibrillator maintenance. Affective Objectives 4-3.44 Defend the reasons for obtaining initial training in automated external defibrillation and the importance of continuing education. 4-3.45 Defend the reason for maintenance of automated external defibrillators. 4-3.46 Explain the rationale for administering nitroglycerin to a patient with chest pain or discomfort. Psychomotor Objectives (1 of 2) 4-3.47 Demonstrate the assessment and emergency medical care of a patient experiencing chest pain/discomfort. 4-3.48 Demonstrate the application and operation of the automated external defibrillator. 4-3.49 Demonstrate the maintenance of an automated external defibrillator. 4-3.50 Demonstrate the assessment and documentation of patient response to the automated external defibrillator. Psychomotor Objectives (2 of 2) 4-3.51 Demonstrate the skills necessary to complete the Automated Defibrillator: Operator’s Shift Checklist. 4-3.52 Perform the steps in facilitating the use of nitroglycerin for chest pain or discomfort. 4-3.53 Demonstrate the assessment and documentation of patient response to nitroglycerin. 4-3.54 Practice completing a prehospital care report for patients with cardiac emergencies. Cardiovascular Emergencies • Cardiovascular disease (CVD) claimed 931,108 lives in the US during 2001. – 2,551 per day – Almost two people per minute! • CVD accounts for 38.5% of all deaths. – One of every 2.6 deaths Blood Flow Through the Heart Electrical System of the Heart Coronary Arteries Blood Flow Blood Cardiac Compromise • Chest pain results from ischemia • Ischemic heart disease involves decreased blood flow to the heart. • If blood flow is not restored, the tissue dies. Atherosclerosis • Materials build up inside blood vessels. • This decreases or obstructs blood flow. • Risk factors place a person at risk. Angina Pectoris • Pain in chest that occurs when the heart does not receive enough oxygen • Typically crushing or squeezing pain • Rarely lasts longer than 15 minutes • Can be difficult to differentiate from heart attack Heart Attack • Acute myocardial infarction (AMI) • Pain signals death of cells. • Opening the coronary artery within the first hour can prevent damage. • Immediate transport is essential. Signs and Symptoms • Sudden onset of weakness, nausea, sweating without obvious cause • Chest pain/discomfort – Often crushing or squeezing – Does not change with each breath • Pain in lower jaw, arms, back, abdomen, or neck • Sudden arrhythmia with syncope • Shortness of breath or dyspnea • Pulmonary edema • Sudden death Pain of Heart Attack • May or may not be caused by exertion • Does not resolve in a few minutes • Can last from 30 minutes to several hours • May not be relieved by rest or nitroglycerin Sudden Death • 40% of AMI patients do not reach the hospital. • Heart may be twitching. Arrhythmias Bradycardia Ventricular Tachycardia Cardiogenic Shock • Heart lacks power to force blood through the circulatory system. • Onset may be immediate or not apparent for 24 hours after AMI. Congestive Heart Failure • • • • • CHF occurs when ventricles are damaged. Heart tries to compensate. Increased heart rate Enlarged left ventricle Fluid backs up into lungs or body as heart fails to pump. You are the Provider • You are a volunteer EMT-B in a rural area. You are dispatched to an older man complaining of severe chest pain. • ALS has been dispatched. • You arrive to find the patient clutching his chest. The pain is the worst he has ever had. • The patient has nitroglycerin but has not taken it yet. • What is wrong with this patient? • What must you know before administering any medication? • What must you specifically know before assisting a patient with nitroglycerin? You are the Provider (continued) Scene Size-up • Scene size-up • General impression – Is the patient responsive? Initial Assessment • Chief complaint on responsive patients • A chief complaint of chest discomfort, shortness of breath, or dizziness must be taken seriously. • Airway and breathing • Circulation Transport Decision • Is the patient a life threat? • Stable patients – Transport in gentle manner. – Avoid lights and siren. – Do not let patient exert or strain self. • Specialty facilities • You obtain a brief history while taking the patient’s blood pressure. • Your partner retrieves the nitroglycerin and obtains permission from medical control. • Your partner administers the nitroglycerin. • What else can you do at this time? You are the Provider (continued) Focused History and Physical Exam • • • • SAMPLE OPQRST Medications are important! Medications often prescribed for CHF: – Furosemide – Digoxin – Amiodarone Focused Physical Exam • • • • Cardiac and respiratory systems Look for skin changes. Lung sounds Baseline vital signs – BOTH systolic and diastolic BP readings Communication Relay history, vital signs, changes, medications, and treatments. Aspirin • Administer according to local protocol. • Prevents clots from becoming bigger • Normal dosage is from 162 to 324 mg. Nitroglycerin • Forms – Pill, spray, skin patch • Effects – Relaxes blood vessel walls – Dilates coronary arteries – Reduces workload of heart Nitroglycerin Contraindications • Systolic blood pressure of less than 100 mm Hg • Head injury • Maximum dose taken in past hour Nitroglycerin Potency • Nitroglycerin loses potency over time. – Especially if exposed to light • When nitroglycerin tablets lose potency: – May not feel the fizzing sensation – May not experience the burning sensation and headache • Fizzing only occurs with a potent tablet, not in the spray form. Assisting With Nitroglycerin (1 of 4) • Obtain order from medical direction. • Take patient’s blood pressure. Assisting With Nitroglycerin (2 of 4) • Check that you have right medication, patient, and delivery route. • Check expiration date. • Find out last dose taken and effects. • Be prepared to lay the patient down. Assisting With Nitroglycerin (3 of 4) • Administer tablet or spray under tongue. • Have patient keep mouth closed until tablet dissolves or is absorbed. Assisting With Nitroglycerin (4 of 4) • • • • Recheck blood pressure. Record each activity and time of application. Reevaluate and note response. May repeat dose in 3 to 5 minutes. Detailed Physical Exam • Perform if time allows. • Do not gather information unless: – Patient’s condition is stable – Everything else is done Ongoing Assessment • • • • Repeat initial assessment. Reassess vital signs every 5 minutes. Monitor closely. If cardiac arrest occurs, begin defibrillation or CPR immediately. • Record interventions, instructions from medical control, patient’s response. • Obtain medical control physician’s signature. You are the Provider (continued) • ALS arrives and you report your interventions and vital signs. • ALS performs cardiac monitoring and prepares for morphine administration. • The patient’s pain is gone by the time you reach the hospital. Heart Surgeries and Pacemakers • Coronary artery bypass graft (CABG) • Angioplasty • Cardiac pacemaker Automatic Implantable Cardiac Defibrillators (1 of 2) • Maintains a regular heart rhythm and rate • Do not place AED patches over pacemaker. Automatic Implantable Cardiac Defibrillators (2 of 2) • Monitor heart rhythm and deliver shocks as needed. • Low electricity will not affect rescuers. Cardiac Arrest • The complete cessation of cardiac activity, either electrical, mechanical, or both. Automated External Defibrillator (AED) • AEDs come in various models. • Some operator interaction required. • A specialized computer recognizes heart rhythms that require defibrillation. Potential AED Problems • Battery is dead. • Patient is moving. • Patient is responsive and has a rapid pulse. AED Advantages • ALS providers do not need to be on scene. • Remote, adhesive defibrillator pads are used. • Efficient transmission of electricity Non-Shockable Rhythms • Asystole • Pulseless electrical activity Rationale for Early Defibrillation • Early defibrillation is the third link in the chain of survival. • A patient in ventricular fibrillation needs to be defibrillated within 2 minutes. AED Maintenance • Read operator’s manual. • Check AED and battery at beginning of each shift. • Get a checklist from the manufacturer. • Report any failures to the manufacturer and the FDA. Medical Direction • Should approve protocols • Should review AED usage • Should review speed of defibrillation • Should provide review of skills every 3 to 6 months Preparation • • • • • • Make sure the electricity injures no one. Do not defibrillate a patient lying in pooled water. Dry a soaking wet patient’s chest first. Do not defibrillate a patient who is touching metal. Remove nitroglycerin patches. Shave a hairy patient’s chest if needed. Using an AED (1 of 8) • Assess responsiveness. • Stop CPR if in progress. • Check breathing and pulse. • If patient is unresponsive and not breathing adequately, give two slow ventilations. Using an AED (2 of 8) • If there is a delay in obtaining an AED, have your partner start or resume CPR. • If an AED is close at hand, prepare the AED pads. • Turn on the machine. Using an AED (3 of 8) • Remove clothing from the patient’s chest area. Apply pads to the chest. • Stop CPR. • State aloud, “Clear the patient.” Using an AED (4 of 8) • Push the analyze button, if there is one. • Wait for the computer. • If shock is not needed, start CPR. • If shock is advised, make sure that no one is touching the patient. • Push the shock button. Using an AED (5 of 8) • After the shock is delivered, begin 5 cycles of CPR, beginning with chest compressions. • After 5 cycles, reanalyze patient’s rhythm. • If the machine advises a shock, clear the patient and push shock button. • If no shock advised, check for pulse. Using an AED (6 of 8) • If the patient has a pulse, check breathing. • If the patient is breathing adequately, provide oxygen via nonrebreathing mask and transport. Using an AED (7 of 8) • If the patient is not breathing adequately, use necessary airway adjuncts and proper positioning to open airway. • Provide artificial ventilations with highconcentration oxygen. • Transport. Using an AED (8 of 8) • If the patient has no pulse, perform 2 minutes of CPR. • Gather additional information on the arrest event. • After 2 minutes of CPR, make sure no one is touching the patient. • Push the analyze button again (as applicable). • If necessary, repeat alternating CPR/Analyze/Shock until ALS arrives. • Transport and check with medical control. • Continue to support the patient as needed. After AED Shocks • • • • Check pulse. No pulse, no shock advised No pulse, shock advised If a patient is breathing independently: – Administer oxygen. – Check pulse. • If a patient has a pulse but breathing is inadequate, assist ventilations. Transport Considerations • Transport: – When patient regains pulse – After delivering six to nine shocks – After receiving three consecutive “no shock advised” messages • Keep AED attached. • Check pulse frequently. • Stop ambulance to use an AED. Cardiac Arrest During Transport (1 of 2) • Check unconscious patient’s pulse every 30 seconds. • If pulse is not present: – Stop the vehicle. – Perform CPR until AED is available. – Analyze rhythm. – Deliver shock(s). – Continue resuscitation according to local protocol. Cardiac Arrest During Transport (2 of 2) • If patient becomes unconscious during transport: – Check pulse. – Stop the vehicle. – Perform CPR until AED is available. – Analyze rhythm. – Deliver up to three shocks. – Continue resuscitation according to local protocol. Review 1. While palpating the radial pulse of a 56-year-old man with chest pain, you note that the pulse rate is 86 beats/min and irregular. This indicates: A. pain. B. fear. C. anxiety. D. a dysrhythmia. Review Answer: D Rationale: An irregular pulse in a patient with a cardiac problem suggests a dysrhythmia—an abnormality in the heart’s electrical conduction system. Patients with signs of cardiac compromise, who have an irregular pulse, must be monitored closely for cardiac arrest. Review 1. While palpating the radial pulse of a 56-year-old man with chest pain, you note that the pulse rate is 86 beats/min and irregular. This indicates: A. pain. Rationale: Pain could be a result or symptom of cardiac ischemia. B. fear. Rationale: Fear of impending death is usually the psychological result of having chest pain. C. anxiety. Rationale: Anxiety is also a symptom of a cardiac event. D. a dysrhythmia. Rationale: Correct answer Review 2. An elderly woman has severe chest pain. She took three nitroglycerin tablets prior to your arrival, but is still in pain. You assess her vital signs and find that her blood pressure is 70/40 mm Hg. What is MOST significant about her blood pressure? A. It is a common finding in the elderly. B. It is a side effect of the nitroglycerin. C. It indicates a decreased cardiac output. D. It is a response to her fear and anxiety. Review Answer: C Rationale: Hypotension in a patient with suspected cardiac compromise indicates significant damage to the heart—usually the left ventricle—and a decrease in cardiac output. Although nitroglycerin can cause hypotension because of its vasodilator effects, hypotension in a cardiac patient should be presumed to be a sign of cardiac damage. Review (1 of 2) 2. An elderly woman has severe chest pain. She took three nitroglycerin tablets prior to your arrival, but is still in pain. You assess her vital signs and find that her blood pressure is 70/40 mm Hg. What is MOST significant about her blood pressure? A. It is a common finding in the elderly. Rationale: Hypertension is a condition more commonly associated with geriatric patients, more so than hypotension. B. It is a side effect of the nitroglycerin. Rationale: Although nitroglycerin can cause hypotension because of its vasodilator effects, hypotension in a cardiac patient should be presumed to be a sign of cardiac damage. Review (2 of 2) 2. An elderly woman has severe chest pain. She took three nitroglycerin tablets prior to your arrival, but is still in pain. You assess her vital signs and find that her blood pressure is 70/40 mm Hg. What is MOST significant about her blood pressure? C. It indicates a decreased cardiac output. Rationale: Correct answer D. It is a response to her fear and anxiety. Rationale: A possibility, but EMS providers must have a high index of suspicion and presume it to be a sign of cardiac damage. Review 3. A patient with cardiac arrest secondary to ventricular fibrillation has the greatest chance for survival if: A. CPR is initiated within 10 minutes. B. oxygen and rapid transport are provided. C. defibrillation is provided within 2 minutes. D. paramedics arrive at the scene within 5 minutes. Review Answer: C Rationale: Survival from cardiac arrest secondary to ventricular fibrillation (V-fib) is highest if CPR is provided immediately and defibrillation is provided within 2 minutes of the patient’s cardiac arrest. Early high-quality CPR and defibrillation are the two most important factors that influence survival from cardiac arrest. Review 3. A patient with cardiac arrest secondary to ventricular fibrillation has the greatest chance for survival if: A. CPR is initiated within 10 minutes. Rationale: CPR needs to be initiated immediately. B. oxygen and rapid transport are provided. Rationale: Oxygen therapy and transport are important parts of resuscitation, but CPR and early defibrillation afford the greatest chance of survivability. C. defibrillation is provided within 2 minutes. Rationale: Correct answer D. paramedics arrive at the scene within 5 minutes. Rationale: Not absolutely necessarily, CPR and early defibrillation will provide the greatest chance of survivability. Review 4. All of the following are common signs and symptoms of cardiac ischemia, EXCEPT: A. headache. B. chest pressure. C. shortness of breath. D. anxiety or restlessness. Review Answer: A Rationale: Cardiac ischemia occurs when the heart’s demand for oxygen exceeds the available supply. Common signs and symptoms of cardiac ischemia include chest pain or discomfort, shortness of breath (dyspnea), and anxiety or restlessness. Headache is not a common symptom of cardiac ischemia. Review 4. All of the following are common signs and symptoms of cardiac ischemia, EXCEPT: A. headache. Rationale: Correct answer B. chest pressure. Rationale: Chest pressure is a definite symptom of a cardiac event. C. shortness of breath. Rationale: This is a response to decreased cardiac output and hypoxia. D. anxiety or restlessness. Rationale: This is caused by a fear of death and is a result of hypoxia, decreased cardiac output, and ischemia. Review 5. A 59-year-old woman presents with chest pressure. She is conscious and alert, but her skin is cool, pale, and clammy. Your first step in providing care (treatment) should be: A. apply the AED. B. administer high-flow oxygen. C. ask her if she takes nitroglycerin. D. take a complete set of vital signs. Review Answer: B Rationale: Any patient with suspected cardiac compromise should be given high-flow oxygen as soon as possible. Obtaining vital signs and inquiring about the use of nitroglycerin are appropriate; however, you should administer oxygen first. The AED is only applied to patients in cardiac arrest. Review 5. A 59-year-old woman presents with chest pressure. She is conscious and alert, but her skin is cool, pale, and clammy. Your first step in providing care (treatment) should be: A. apply the AED. Rationale: The AED is only applied to patients in cardiac arrest. B. administer high-flow oxygen. Rationale: Correct answer C. ask her if she takes nitroglycerin. Rationale: Inquiring about the use of nitroglycerin is appropriate, but not the first step. D. take a complete set of vital signs. Rationale: Obtaining vital signs is important, but not the first step. Review 6. When using the AED to defibrillate a patient in cardiac arrest, you should: A. analyze the cardiac rhythm every 60 seconds. B. check for a pulse following each defibrillation. C. deliver up to three shocks in a row if indicated. D. immediately resume CPR following defibrillation. Review Answer: D Rationale: When using the AED on a cardiac arrest patient, deliver a single shock if indicated and immediately resume CPR, starting with chest compressions. Perform 5 cycles (about 2 minutes) of CPR and then reanalyze the patient’s cardiac rhythm. Review 6. When using the AED to defibrillate a patient in cardiac arrest, you should: A. analyze the cardiac rhythm every 60 seconds. Rationale: A cardiac rhythm is checked initially and then after every 2 minutes of CPR. B. check for a pulse following each defibrillation. Rationale: The pulse is assessed before CPR is initiated. C. deliver up to three shocks in a row if indicated. Rationale: Only one shock is delivered followed by 2 minutes of CPR. D. immediately resume CPR following defibrillation. Rationale: Correct answer Review 7. After administering a nitroglycerin tablet to a patient, the EMT-B should: A. check the expiration date of the nitroglycerin. B. reassess the patient’s blood pressure within 5 minutes. C. instruct the patient to chew the tablet until it is dissolved. D. ensure that the nitroglycerin is prescribed to the patient. Review Answer: B Rationale: Nitroglycerin is a vasodilator and can lower the patient’s BP; therefore, you should reassess the patient’s BP within 5 minutes after giving nitroglycerin. Instruct the patient to allow the nitroglycerin to dissolve under his or her tongue; it should not be chewed. You should check the drug’s expiration date and ensure that it is prescribed to the patient before administering it. Review 7. After administering a nitroglycerin tablet to a patient, the EMT-B should: A. check the expiration date of the nitroglycerin. Rationale: This is checked before medication administration. B. reassess the patient’s blood pressure within 5 minutes. Rationale: Correct answer C. instruct the patient to chew the tablet until it is dissolved. Rationale: The tablet is placed under the patient’s tongue and allowed to dissolve. D. ensure that the nitroglycerin is prescribed to the patient. Rationale: This is checked before medication administration. Review 8. If a patient with an implanted pacemaker is in cardiac arrest, the EMT-B should: A. avoid defibrillation with the AED and transport at once. B. not apply the AED until he or she contacts medical control. C. place the AED pads at least 1” away from the pacemaker. D. apply the AED pads directly over the implanted pacemaker. Review Answer: C Rationale: The only modification required for cardiac arrest patients with an implanted pacemaker is to ensure that the AED pads are at least 1” away from the pacemaker. Placing the AED pads directly over the pacemaker will result in a less effective defibrillation and may damage the pacemaker. Review 8. If a patient with an implanted pacemaker is in cardiac arrest, the EMT-B should: A. avoid defibrillation with the AED and transport at once. Rationale: Early defibrillation is the most important step. Do not withhold it. B. not apply the AED until he or she contacts medical control. Rationale: Implanted pacemakers are not a contraindication to using an AED. C. place the AED pads at least 1” away from the pacemaker. Rationale: Correct answer D. apply the AED pads directly over the implanted pacemaker. Rationale: Placing the AED pads directly over the pacemaker will result in a less effective defibrillation and may damage the pacemaker. Review 9. Nitroglycerin is contraindicated in patients: A. with a systolic blood pressure less than 100 mm Hg. B. with chest pain of greater than 30 minutes duration. C. who are currently taking antibiotics for an infection. D. who are less than 40 years of age and have diabetes. Review Answer: A Rationale: Nitroglycerin is a vasodilator and may cause a drop in BP; therefore, it is contraindicated in patients with a systolic BP of less than 100 mm Hg and in patients who have taken erectile dysfunction (ED) drugs (eg, Viagra, Cialis, Levitra) within the past 24 to 36 hours. ED drugs are also vasodilators; if given in combination with nitroglycerin, severe hypotension may occur. Review 9. Nitroglycerin is contraindicated in patients: A. with a systolic blood pressure less than 100 mm Hg. Rationale: Correct answer B. with chest pain of greater than 30 minutes duration. Rationale: Cardiac chest pain is the primary indication for the use of nitroglycerin. C. who are currently taking antibiotics for an infection. Rationale: Antibiotics are not a contraindication for nitroglycerin use. Prior adverse reactions to the drug and the use of other nitrates would be a contraindication. D. who are less than 40 years of age and have diabetes. Rationale: While the patient’s age must be considered, it is not a contraindication. Review 10. A 56-year-old man has an acute myocardial infarction. Which of the following blood vessels became blocked and led to his condition? A. Coronary veins B. Coronary arteries C. Pulmonary veins D. Pulmonary arteries Review Answer: B Rationale: The coronary arteries, which branch off the aorta, supply the myocardium (heart muscle) with oxygen-rich blood. Occlusion of one or more of these arteries results in a cessation of oxygenated blood beyond the area of occlusion and results in acute myocardial infarction (AMI). Review 10. A 56-year-old man has an acute myocardial infarction. Which of the following blood vessels became blocked and led to his condition? A. Coronary veins Rationale: Coronary veins do not carry oxygen and would not be the direct cause of an acute MI. B. Coronary arteries Rationale: Correct answer C. Pulmonary veins Rationale: Pulmonary veins are the primary blood supply to the lungs and not the heart. D. Pulmonary arteries Rationale: Pulmonary arteries are the route of blood return to the left atrium from the lungs. An obstruction would not cause an acute MI.