An intoxicated 25 year old student awakes the morning after the final examinations. While lying supine, he vomits and aspirates stomach contents. Several days later, after developing a high fever and coughing purulent sputum, he seeks medical attention. The chest X-Rays demonstrate an early consolidating pneumonia. The region most likely involved is the ______?
Superior segment, right lower lobe. In the supine position, the most gravity dependent segmental bronchus is the superior segment of the right inferior lobe. In this case, it is therefore the most likely site of aspiration pneumonia.
A 23 year-old male is brought to your emergency room following a stab wound. Anatomically, you note a well-demarcated, horizontal, 5 cm laceration just to right of the sternum, at approximately 6 centimeters below the sternal angle (of Louis). His findings include: blood pressure 72/40; heart rate 120/min, regular; distended neck veins; clear lung fields via auscultation; and muffled (distant) heart sounds (so-called “Beck’s Triad”). Due to the location of the wound, you suspect a _______?
Cardiac Tamponade. In the presence of bleeding from a stab wound to the heart, pressure around the heart gradually increases as blood leaks from the affected cardiac chamber. This increasing pressure eventually prevents the heart from filling normally and cardiac output falls (hence the drop in blood pressure and cardiac output). The pressure backs up, causing the large veins to dilate (distention of the neck veins), and the increasing layer of blood in the pericardium muffles the heart sounds. This can rapidly cause acute cardiac arrest and death.
You have given a patient a new drug whose only effect is that it prevents only the funny sodium channels (if) in the heart from opening. What effect will this drug have on the heart rate?
Funny Na+ channels help depolarize the nodal action potential to threshold. One consequence of blocking these channels would be to slow the rise of the nodal pacemaker potential toward threshold. This would increase the interval between nodal action potentials and slow the heart.
A 77 year old male with a history of heart failure comes in today and on his electrocardiogram shows atrial fibrillation (the atria are not contracting). On prior exams he has had a normal S1, normally split S2 and an S3 and S4. You note that one of these heart sounds is missing. Which one?
S4 is the heart sound produced by the contraction of the atria usually found in somewhat noncompliant (stiff hearts in patients with hypertension). In this case however the patient is in atrial fibrillation in which the atria are fibrillating and there is no organized atrial contraction. Hence the S4 will be absent in patients with atrial fibrillation.
Your patient starts to take a new medication that has a side-effect to inhibit cardiac voltage dependent potassium channels (IKr and IKs). What change would you expect to observe in the ECG?
Prolongation of the QTc interval. The QT interval represents repolarization of the ventricles. Ventricular repolarization is controlled by the rapidly (IKr) and slowly (IKs) activating delayed rectifier potassium channels. Decreases in activity of either channel will prolong the QT interval.
Drug X is...
Metoprolol. Metoprolol is a beta-1 selective antagonist. In the figure on left, Epi (apparently a low dose) is causing an increase in HR (beta-1 effect), a drop in diastolic BP (a beta-2 effect), and an increase in pulse pressure (the difference between diastolic and systolic pressure that is due mostly to beta-1 stimulated increase in HR and contractile force). After drug X is given, Epi no longer stimulates HR (beta-1 effect), and Epi no longer increases the pulse pressure (also a beta-1 effect). However, Epi continues to cause a drop in the diastolic pressure (a beta-2 effect). So, drug X must be a selective beta-1 antagonist, and metoprolol is the only beta-1 selective antagonist.
Evaluate the mean QRS axis in your patient presenting with the following ECG.
Determining the mean QRS axis from an EKG requires measurements in two leads. Looking at lead I, the mean QRS axis is positive. If we look at lead aVF, the mean QRS axis is negative. Referencing the hexaxial diagram, a positive mean QRS axis in lead I and a negative mean QRS axis in lead aVF would fall between 0 and -90 degrees.
Mr Jones comes to the Emergency Department with chest pain and shortness of breath. His 12 lead ECG and blood enzyme levels show an acute infarction in the inferior, posterior area of the left ventricle. Cardiac catheterization reveals a clot. His hemodynamic parameters are listed below. After a clot dissolving drug is infused into the coronary artery, the hemodynamics are shown below. Systemic vascular resistance (total peripheral vascular resistance) when he arrives is:
SVR = (mean arterial pressure – right atrial pressure) / Cardiac Output. (70 – 10)/3 = 60/3 = 20
A mother presents with her 1 week old boy to your clinic. The baby was cyanotic at birth with a heart murmur. After further examination you determine that the child already has heart failure. What embryological problems might this child have with blood flow in his heart?
During normal development, neural crest differentiate into the truncus arteriosus and spiral into the aorticopulmonary septum. When it does not spiral, you get TRANSPOSITION of the great vessels. When the atrioventricular septum does not develop properly, you get TETRALOGY OF FALLOT and/or PERSISTENT TRUNCUS ARTERIOSUS.
What embryonic structure gives rise to the outflow tract of the left and right ventricles?
You are performing an intrauterine surgery on a neonate due to heart problems. During the surgery, you note that the ventricles and atria lack trabeculae. What embryonic structes may have a mutation that would cause this?
The primitive ventricles and atria.
You are performing an intrauterine surgery on a neonate that has had irregular heart beats. When doing your surgery, you notice that venous flow from the muscles of the heart is obstructed and the heart beats weakly. What embryonic structure may have a mutation in this child?
Left horn of the sinus venosus. This structure gives rise to the coronary sinus and the SA node. This explains decreased venous flow from the coronary vessels and irregular heart beat because of SA node dysfunction.
What embryological structure forms the smooth part of the right atrium?
The right horn of the sinus venosus.
A patient presents with with decreased cardiac output. EKG shows decreased p-wave and angiogram reveals a narrowed superior vena cava. What embryological structures were likely mutated in this patient?
Right common cardinal vein and right anterior cardinal vein
How does the interventricular septum develop?
Muscular Ventricular Septum develops
Aorticopulmonary Septum spirals to form membranous interventricular septum
Endocardial Cushions fuse to membranous interventricular septum
When dissecting your cadaver, you notice a spot between the left and right atria that is translucent to light. What normally happens during fetal development that makes that portion continuous with surrounding tissue?
Foramen primum narrows as septum primum grows toward endocardial cushions
Perforations in septum primum forms foramen secundum and the foramen primum disappears
Septum secundum grows and upper part of septum primum degenerates
Septum primum forms the valve of the foramen ovale
Septum secundum and septum primum fuse to form the atrial septum
Foramen ovale closes after birth from increase in left atrial pressure.
Young neonates do not have bone marrow until about week 20. Before this, in what locations do neonates carry out hematopoiesis?
Yolk sac (3-10 wks). Liver (6 wks - birth). Spleen (15-30 wks). Bone Marrow (22 wks on). "Young Liver Synthesizes Blood"
You invent a new medical device that can measure neonatal blood pressure. You test out your device and it tells you that the neonate has a higher pressure on the right side of her heart. Should you scrap the device or is this reading likely correct?
The reading is correct. Fetal circulation starts at the umbilical vein, traveling through the ductus venosus, bypassing the liver and going to the heart. Once blood gets to the heart, it is shunted through the ductus arteriosus if it needs to go back to the mother for more oxygen, or through the foramen ovale if it is to be pumped out into circulation. Because of this system, the right heart has more pressure in it.
What are the post-natal derivatives of the following?
- Umbilical vein
- Umbilical arteries
- Ductus arteriosus
- Ductues venosus
- Foramen ovale
Umbilical vein = ligamentum teres hepatis
Umbilical arteries = medial umbilical ligaments
Ductus arteriosus = ligamentum arteriosum
Ductues venosus = ligamentum venosum
Foramen ovale = fossa ovalis
Allantois = urachus-median umbilical ligament
Notocord = nucleus pulposus
A 44 year old obese male presents to your clinic complaining of hoarseness and dysphagia (difficulty swallowing). What cardiac issue could be causing this patient's symptoms?
Left atrail enlargment. Compression of the esophagus (dysphagia) and left recurrent laryngeal nerve (hoarseness) by the left atrium causes these symptoms.
A patient comes to see you with chest pain. On his EKG you note problems in SA and AV node conduction. This patient also has very high cholesterol. How could the cholesterol of this patient be the cause of the findings in the patient's EKG?
The right coronary artery provides blood supply for the SA and AV nodes.
After experiencing mild chest pain and discomfort for the past few months, a patient has a heart attack. What is the most common artery that causes this patient's condition?
The LAD (left anterior decending) artery is the most common coronary artery occlusion.
What determines coronary circulation dominance?
Which artery supplies the posterior decending artery.
- 85% of people have supply from the RCA (right coronary artery) = right-dominant circulation
- 8% of people have supply from the LCX (left coronary circumflex artery) = left-dominant circulation
- 7% of people have supply from the RCA and LCX = codominant circulation
You are performing an angiogram on one of your patients to find the source of coronary artery blockage. When you squirt dye into the catheter, you see the dye run through and outline the coronary arteries. At what point in the cardiac cycle is the heart when you see the dye in the coronary arteries?
Diastole. This is when the coronary arteries fill with blood.
Where do lung alveoli form from in the embryo?
Endoderm. They bud off of the foregut.
A 33 year old patient comes to the ER complaining of chest pain, rapid palpitations and dizziness. She drinks four cups of coffee a day and 2 glasses of wine at night. ECG after the episode reveals paroxysmal ventricular tachycardia. You try the vagal maneuver to terminate the tachycardia, but it doesn't work. What is your first drug of choice to control her PSVT?
Adenosine. It slows conduction at the AV node, slowing action potential initiation in the ventricles.
Calculate vascular resistance if cardiac output is 5L/min, MAP is 108mmHg, left atrial pressure is 12mmHg, right atrial pressure is 8mmHg, stroke volume is 100mL and heart rate is 50 bpm.
Vascular resistance is equal to = change in pressure / flow. (MAP - right atrial pressure) / flow. (108 - 8) / 5 = 20.
If a system filled with water has an outflow of 6 L/min, what would outflow of this sytem be if water was replaced by whole blood with a hematocrit reading of 45?
As hematocrit goes up so does viscosity. Viscosity of blood is about 3-4x that of water. Dividing 6 by 3 = 2.
Mr. Jones comes to the ER with chest pain. His 12 lead ECG and blood enzyme levels show an acute infarction in the posterior inferior portion of the left ventricle. Cardiac catheterization shows a clot. Hemodynamic parameters are shown below when he arrived. Systemic vascular resistance (total peripheral resistance) when he arrives is what?
CO = 3
MAP = 70
Mean Pulmonary Artery Pressure = 24
Right Atrial Pressure = 10
Left Atrial Pressure = 12
Coronary Blood Flow = 10
20. R = change in pressure/ flow. (MAP - right atrial pressure)/ CO. (70-10)/3 = 20.
A previous patient of yours comes to the ER in atrial fibrillation. Previously he had all four heart sounds. Which heart sound will be absent when he comes to the ER in a-fib?
S4 because the atria are no longer contracting. S4 is a sound of stiff atrial valves kicking open.