Cardiac Flashcards
Name the organs in the vessel rich group. What percent of cardiac output goes to each of these organs?
The brain, kidney, liver, lungs, heart, digestive track, and endocrine tissues are organs of the vessel rich group. These are well perfused organs. 25% of the cardiac output goes to the liver. 4-5% goes to the heart. 15% goes to the brain. 20% goes to the kidneys. 100% goes to the lungs.
What nerves carry the aferrant and efferent signals of the Bainbridge reflex? What does the Bainbridge reflex help prevent?
When the great veins and right atrium are stretched by increased vascular volume, stretch receptores send aferrant signals to the medulla via the vagus nerve. The medulla then transmits efferent signals via the sympathetic nerves to increase heart rate (by as much as 75%) and myocardial contractility. The Bainbridge reflex helps prevent damming up of blood in veins, the atrium, and the pulmonary circulation.
Where is the J point in the ECG waveform? How is the J point used in ECG interpretation?
The J point is the point on the ECG when the QRS complex ends and the ST segment begins. ST elevation or depression is measured by comparing lead voltage at 60 or 80 milliseconds after the J point to the isoelectric value, usually measured during the PR interval. ST elevation or depression may also be measured at the J point.
Left bundle branch block and right bundle branch block are both characterized by a heart rate <100 beats per minute, regular rhythm, normal PR interval, QRS complex >120 ms (0.12s), and ST segment and T waves in the opposite direction of the R wave. What features uniquely identify left bundle branch block?
Left bundle branch block is uniquely characterized by a broad sometimes notched R wave in left side leads ( I, AVL, V5, V 6 ), deep S waves in the right precordial leads, and absent septal Q waves.
Left bundle branch block and right bundle branch block are both characterized by a heart rate <100 beats per minute, regular rhythm, normal PR interval, QRS complex >120 ms (0.12s), and ST segment and T waves in the opposite direction of the R wave. What features uniquely identify right bundle branch block?
Right bundle branch block is uniquely characterized by prominent notched R waves with “M” pattern (rabbit ears) and rsr’, rsR’, or rSR’ on the right side leads (aVr, V1) and wide S on the left side leads.
Which is more prevalent right bundle branch block or left bundle branch block? Which is more ominous?
RBBB is common in the general healthy population without clinical evidence of structural heart disease and has no prognostic significance in this group. RBBB occurs in about 1% of hospitalized patients and is much more common than LBBB. LBBB is more ominous. LBBB does not occur in healthy individuals. LBBB is often associated with the ischemic heart disease, hypertension, and valvular heart disease. LBBB obscures or simulates other ECG patterns. In the presence of left bundle branch block, the diagnosis of LVH, acute ischaemia, or myocardial infarction may be difficult or impossible.
What is one concern with pulmonary artery catheter placement in a patient with left bundle branch block?
Insertion of a pulmonary artery catheter may precipitate right bundle branch block, thus insertion of a PAC in a patient with left bundle branch block may precipitate complete heart block (third degree block).
The alpha-2 adrenergic receptor agonist, Clonidine, acts where centrally to produce what therapeutic effect?
Stimulation of alpha-2A receptors of inhibitory neurons in the vasomotor center of the medulla in the brain stem inhibits sympathetic nervous system outflow. This action decreases blood pressure.
Alpha-2 adrenergic receptor agonists antagonize the sympathetic nervous system peripherally. How?
Alpha-2 receptors are found peripherally in the surface membrane of the norepinephrine containing presynaptic nerve terminals of sympathetic postganglionic neurons. Stimulation of these receptors decreases the release of norepinephrine from the presynaptic nerve terminal. This decreased release of norepinephrine contributes modestly to the clonidine-induced decrease in blood pressure.
The patient administered sodium nitroprusside continuously (by drip) presents with the following arterial blood gases: pH = 7.21, PaCO2 = 32, Pa02 = 104, base excess = -10. What is your next action? Explain that arterial blood gases.
Turn off the nitroprusside drip. This ABG suggests cyanide toxicity. The base excess of -10 demonstrates that the acidosis is metabolic. The low PaCO2 of 32 demonstrates partial respiratory compensation of the metabolic acidosis.
Research has validated that use of a single ECG lead for ischemic monitoring in patients with documented seed is inadequate monitoring with multiple leads enhances patient safety. A5 cable ECG monitoring system is currently the standard for monitoring patients with suspected myocardial ischaemia. Describe the placement of the five electrodes in the five cable system.
In the five electrode monitoring system, the four limb electrodes LA, RA, LL, and RL placed at their corresponding monitoring locations allow any of the six bipolar limb leads (I, I, I I, aVr, AVL, and aVf) to be obtained, and a fifth chest electrode can be placed in any of the standard precordial V1 to V6 locations.
Describe the proper placement of RA, LA, LL, and RL electrodes according to the Mason-Likar lead position scheme.
Proper placement of the electrode is over the outer right clavicle and of the LA electrode is over the outer left clavicle. The LL electrode is placed near the left iliac crest or midway between the costal margin and the left iliac crest along the anterior axillary line. The RL electrode may be placed at any convenient location on the body.
Which unipolar lead in the five lead monitoring system is preferred when arrhythmias are anticipated? Which unipolar leads are preferred for monitoring ischemia?
V1 is preferred for special arrhythmia monitoring, whereas V3 to V5 are the preferred leads for monitoring ischemia.
