Cardiology Cases: 40 Cases

cardiology

cases

40 Cases

Clinical Discussions for Medical Students and Residents

Emphasis on the Pathophysiology of Disease

JORGE C. RIOS MD, FACC, FACP

GREGORIO KOSS MD, FACC

NANCY SELFRIDGE MD

Copyright © 2018 by Jorge Rios.

Library of Congress Control Number:     2018906577

ISBN:                Hardcover                      978-1-9845-3119-3

                        Softcover                        978-1-9845-3118-6

                        eBook                             978-1-9845-3117-9

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the copyright owner.

Any people depicted in stock imagery provided by Getty Images are models, and such images are being used for illustrative purposes only.

Certain stock imagery © Getty Images.

Rev. date: 07/28/2018

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CONTENTS

ACKNOWLEDGMENT

INTRODUCTION

CASE NO. 1: FUNCTIONAL MURMUR—REVIEW OF BASIC CONCEPTS

CASE 1 QUESTIONS

VALVULAR HEART DISEASE

CASE NO. 2: MITRAL STENOSIS

CASE 2 QUESTIONS

CASE NO. 3: CHRONIC MITRAL REGURGITATION

CASE 3 QUESTIONS

CASE NO. 4: ACUTE MITRAL REGURGITATION

CASE 4 QUESTIONS

CASE 5 QUESTIONS

CASE NO. 6: TRICUSPID REGURGITATION

CASE 6 QUESTIONS

CASE NO. 7: VALVULAR AORTIC STENOSIS

CASE 7 QUESTIONS

CASE NO. 8: CHRONIC AORTIC REGURGITATION

CASE 8 QUESTIONS

CASE NO. 9: ACUTE AORTIC REGURGITATION

CASE 9 QUESTIONS

CORONARY DISEASE

MYOCARDIAL ISCHEMIA

CASE NO 10: STABLE ANGINA PECTORIS

CASE 10 QUESTIONS

CASE 11 QUESTIONS

CASE NO. 12: VENTRICULAR ANEURYSM

CASE 12 QUESTIONS

CASE NO. 13: UNSTABLE ANGINA

CASE 13 QUESTIONS

CASE NO. 14: ACUTE MI AND HEART BLOCK

CASE 14 QUESTIONS

CASE NO. 15: ACUTE MI HYPOTENSION-CARDIOGENIC SHOCK

CASE 15 QUESTIONS

CASE NO. 16: ACUTE MYOCARDIAL INFARCTION—HYPOTENSION

CASE 16 QUESTIONS

CASE NO. 17: UNSTABLE ANGINA PECTORIS

CASE 17 QUESTIONS

CASE NO. 18: ORTHOSTATIC HYPOTENSION IN A POST-MI HYPERTENSIVE PATIENT

CASE 18 QUESTIONS

CASE NO 19: POST-MI VENTRICULAR TACHYCARDIA

CASE 19 QUESTIONS

CARDIOMYOPATHIES

HEART FAILURE

CASE NO. 20: POSTPARTUM HEART FAILURE—DILATED CARDIOMYOPATHY

CASE 20 QUESTIONS

CASE NO. 21: HYPERTENSION—DIASTOLIC HEART FAILURE

CASE 21 QUESTIONS

CASE NO. 22: RESTRICTIVE CARDIOMYOPATHY

CASE 22 QUESTIONS

CASE NO. 23: OBSTRUCTIVE CARDIOMYOPATHY

CASE 23 QUESTIONS

PERICARDIAL DISEASE

CASE NO. 24: CARDIAC TAMPONADE

CASE 24 QUESTIONS

CASE NO. 25. CONSTRICTIVE PERICARDITIS

CASE 25 QUESTIONS

CARDIAC ARRHYTHMIAS

CASE NO. 26: COMPLETE HEART BLOCK

CASE 26 QUESTIONS

CASE NO. 27: BRADYARRHYTHMIAS—SICK SINUS SYNDROME

CASE 27 QUESTIONS

CASE NO. 28: WENCKEBACH PHENOMENA

CASE 28 QUESTIONS

CASE NO. 29: MOBITZ 2

CASE 29 QUESTIONS

CASE NO. 30: SUPRAVENTRICULAR TACHYCARDIA

CASE 30 QUESTIONS

CASE NO. 31: WOLFF-PARKINSON-WHITE SYNDROME

CASE 31 QUESTIONS

CASE NO. 32: ATRIAL FIBRILLATION

CASE 32 QUESTIONS

CASE NO. 33: ATRIAL FLUTTER

CASES 32–33 QUESTIONS

CASE NO. 34: LONG QT INTERVAL

CASE 34 QUESTIONS

CONGENITAL HEART DISEASE

CASE NO. 35: PATHOPHYSIOLOGY OF LEFT TO RIGHT SHUNTS—VENTRICULAR SEPTAL DEFECT

CASE 35 QUESTIONS

CASE NO. 36: ATRIAL SEPTAL DEFECT

CASE 36 QUESTIONS

CASE NO. 37: PATENT DUCTUS ARTERIOSUS

CASE 37 QUESTIONS

CASE NO. 38: CONGENITAL CARDIAC DEFECT AND PULMONARY HYPERTENSION

CASE 38 QUESTIONS

CASE NO. 39: CYANOTIC HEART DISEASE—TETRALOGY OF FALLOT

CASE 39 QUESTIONS

CASE NO. 40: PULMONARY STENOSIS

CASE 40 QUESTIONS

CORRECT ANSWERS

SELECTED REFERENCES

ACKNOWLEDGMENT

To the many patients that over many years allowed our students to learn by hearing their medical secrets and their physical finding continued to give us the inspirations.

To the thousands of students that over the many years continued to give us the inspiration to do what we did

To our families, that always provided us the support to continue doing what we have loved the most

INTRODUCTION

Medical education has changed. The artificial division between basic sciences and clinical sciences practiced in medical schools has eroded and is replaced by teaching approaches where clinical examples are used to explain the application of basic science principles and vice versa. At the same time, clinical discussions often include reviews of the basic sciences taught earlier during the first years of medical school. This approach facilitates understanding of the mechanism of diseases and provides a more scientific content.

We hope to achieve the same goal, presenting actual clinical cases that allow review of basic concepts and principles of cardiac physiology and how they explain the pathophysiology applicable to the case.

This is not a textbook. We will present cardiac cases that represent various pathologies encountered in clinical practice. These cases are often encountered in the daily clinical setting or discussed on bedside rounds or in resident reports. Our emphasis is on the mechanism of disease and alterations on physiology with minimal discussion on the diagnostic technology commonly used. The content of each case will prepare the resident or student for the discussion likely to happen in those settings.

At the end of each case, we will present a number of practice questions relevant to the manifestations of the disease and the pathophysiology. Answers will be found in a separate chapter at the end.

We have included references. We present a list of traditional textbooks that can provide greater depth in the discussion, and for each case, we offer a list of articles that allow more extensive review of each topic.

We hope that students and residents find this book useful and practical.

CASE NO. 1: FUNCTIONAL MURMUR—REVIEW

OF BASIC CONCEPTS

A twenty-five-year-old female on the third trimester of an uncomplicated pregnancy is seen by her obstetrician. Her past medical history is noncontributory, and on close questioning, she denies any symptoms commonly associated with heart disease. In the past, she had been told by her primary care physician that she had no cardiac murmurs.

On physical examination, heart rate was 100x’, no evidence of ventricular hypertrophy, and all pulses were normal but slightly bounding. Jugular pulse was normal. Auscultation revealed a slightly louder S1, normal splitting of S2, and a very soft, low frequency S3. A grade 2 ejection systolic murmur was best heard at the second left interspace without radiation. The remainder of the cardiovascular examination was unremarkable.

ECG and chest x-ray were normal.

DISCUSSION

The clinical presentation and physical findings and her past medical history suggest a normal individual with physiological changes and physical findings associated with pregnancy. We will also review some basic concepts of cardiac physiology learned in the first year of medical school that apply to this and the other cases. They are critical in understanding most cardiac diseases.

What changes in cardiovascular physiology occur during pregnancy?

Pregnancy results in multiple changes in cardiovascular physiology, and they begin as early as the eighth week of pregnancy.

• Cardiac output increases by 20% and up to 40%. The maximum cardiac output is found at about 20–28 weeks’ gestation. There is a minimal fall at term.

• The increase in cardiac output results from increased stroke volume and heart rate.

• Peripheral vasodilatation is the most likely cause of changes in cardiac output. Peripheral vascular resistance decreases by 25–30% with the consequent increase in cardiac output.

• These changes are mediated by endothelium-dependent factors, such as nitric oxide synthesis, upregulated by estradiol and possibly prostaglandins.

• Increase in stroke volume is possible due to the early increase in ventricular end-diastolic volume seen in pregnancy.

• The heart is physiologically dilated, and myocardial contractility is increased.

• Although stroke volume declines toward term, the increase in maternal heart rate (10–20 beats per minute) is maintained, thus preserving the increased cardiac output.

• Blood pressure decreases in the first and second trimesters but increases to nonpregnant levels in the third trimester.

• Pulmonary capillary wedge pressure and central venous pressure do not increase significantly.

• Pulmonary vascular resistance (PVR), like systemic vascular resistance (SVR), decreases significantly.

• Serum osmotic pressure is reduced by 10–15%.

• Maternal position alters hemodynamics in advanced pregnancy. In the supine position, pressure of the uterus on the inferior vena cava (IVC) causes a reduction in venous return to the heart and a potential fall in cardiac output.

• After delivery, cardiac output increases, followed by a rapid decline to prepartum values.

The above physiological changes affect findings in the cardiovascular examination that may be misinterpreted as pathological, such as

• Bounding or collapsing arterial pulse.

• An ejection systolic murmur, present in over 90% of pregnant women. The murmur may be loud and audible all over the precordium.

• A loud first heart sound caused by increased contractility.

• A third heart sound secondary to increased cardiac output.

• A continuous murmur over breast tissue secondary to increased flow over the breasts.

The discussion above motivates a review of some basic physiological concepts applicable to day-to-day clinical practice.

CARDIAC OUTPUT

Cardiac output is expressed in liters per minute and is calculated through various methods (Fick principle, thermodilution, echocardiography, etc.).

The main factors that determine cardiac output include heart rate and stroke volume.

REGULATION OF THE HEART RATE

The regulation of heart rate rests on parasympathetic and sympathetic effects.

• At rest, balance between parasympathetic and sympathetic maintains heart rate down to around 60–70 beats per minute. At night, further decrease in heart rate can be noted.

• An increase in heart rate is secondary to the release of norepinephrine that increases the slope of phase 4 of the pacemaker potential by opening Ca++ channels. The pacemaker reaches threshold potential faster, and the heart rate is increased.

REGULATION OF STROKE VOLUME

Stroke volume is the amount of blood discharged by the ventricle on each systole and is calculated. as

Stroke volume = cardiac output / heart rate

What are important factors that influence stroke volume?

• Sympathetic effect. Norepinephrine increases the force of contraction by increasing the Ca++ effect. This would increase ejection fraction and stroke volume.

• Afterload. Aortic pressure is referred as afterload because it is the load experienced by the ventricle after it begins contracting.

• Frank-Starling mechanism. Heart muscle fibers respond to stretch by increasing contractility. Changes in the end-diastolic volume result in an increase in stroke volume due to an increased expenditure of ATP.

What other factors influence contractility? How is contractility changed?

The release of catecholamine determines the concentration of calcium ions in a cardiac muscle cell. The increased force of contraction depends on the concentration of calcium ions in the cell. This results in increased binding of myosin and actin.

Some factors in the control of contractility include the following:

• Increased circulating levels of catecholamines. This causes the receptors to activate adenylate cyclase and increase CAM, phosphorylating phospholamban (via protein kinase A).

• Phosphorylating phospholamban. When phospholamban is not phosphorylated, it inhibits the calcium pumps. When levels of calcium stored in the sarcoplasmic reticulum are increased, it allows a higher rate of calcium release at the next contraction.

• Troponin-C is sensitized to the effects of calcium.

• Phosphorylating L-type calcium channels increase the permeability to calcium, increasing contractility.

Changes in cardiac contractility shift the entire Frank-Starling curve. The curve shifts upward when contractility increases and downward if contractility decreases.

How are changes in contractility influence clinical examination?

- Increased contractility results in faster upstroke of the ventricular pressure curve during isometric contraction. This is often accompanied by a brisk, faster arterial pulse upstroke.

- S1 is louder. The loudest component of S1 is related to closure of the mitral and tricuspid valves. Softer, lower frequency components are caused by myocardial contractility. In the case of increase rate of contractility, such as exercise or anemia, the myocardial component of the first sound increases in intensity.

Why is there a difference in timing in the closure of aortic and pulmonary valves?

The left ventricular wall faces a stronger resistance and creates stronger contractile force than that of the right ventricle, resulting in earlier closure. Also, the inspiratory changes in right ventricular volume change during causes an increased duration of systole.

ADDITIONAL SOUNDS GENERATED

A supple ventricular myocardium undergoes rapid expansion, creating a low frequency sound at the end of rapid ventricular filling. An S3 is a normal finding in young people, especially those with a high cardiac output state. S4 is not observed in normal individuals since it represents decreased compliance of the ventricles.

THE PRESSURE VOLUME CURVE

The pressure/volume curve is a simple and graphic way to describe the changes in pressure and volume occurring during the cardiac cycle.

Fig. 1.1. In the horizontal axis, we observe changes in ventricular volume and changes in pressure in the vertical axis. The stroke volume is represented by the volume changes between isovolumetric contraction and isovolumetric relaxation.

Understanding the pressure/volume loop facilitates the understanding of the pathophysiology of cardiac lesions. If students understand and remember the pressure/volume curve, they can explain the pathophysiology of most lesions.

How do cardiac murmurs originate?

An early and brief ejection murmur, as observed in pregnancy, is usually not indicative of heart disease, but it is related to increase cardiac flow. The increased flow generates turbulence.

Murmurs are caused by turbulence. Under normal circumstances, blood flow is laminar, characterized by concentric layers of blood moving in parallel down the length of the vessel. The orderly movement of adjacent layers of blood flow through a vessel helps reduce energy loss. Disruption of laminar flow leads to turbulence and increased energy losses.

High velocities of flow and low blood viscosity (occurs with chronic anemia) are more likely to cause turbulence. Turbulence does not begin to occur until the velocity of flow becomes high enough that the flow lamina breaks apart. At this point, turbulence develops.

Turbulence generates sound waves (i.e., ejection murmurs, carotid bruits, etc.). Because higher velocities enhance turbulence, murmurs intensify as flow increases. These can result from

• high cardiac output, even across anatomically normal valves;

• a decrease in blood viscosity; and

• increasing degree of obstruction.

As illustrated by this case, a high cardiac output may cause new and functional murmurs. The increased flow and the decreased viscosity are proper explanations of the origin of the murmur.

When does the highest flow velocity occur in a healthy heart?

Velocity of flow is at its highest in the first half of systole. That explains the development of turbulence and the development of a functional murmur in early systole.

Several other hemodynamic calculations are commonly used and are of special significance in understanding the pathophysiology of cardiac diseases. The student will encounter application of these concepts especially while rotating through intensive care or cardiac care units.

• Cardiac output is the amount of blood the heart pumps in one minute, expressed in liters per minute.

Related calculations derived from cardiac output determinations include the following:

• Cardiac index expresses cardiac output as a function of body surface area. The formula is as follows:

Cardiac output (liters/minute) / body surface area (in m2)

• Stroke volume is the amount ejected from the ventricles per heartbeat. The formula is as follows:

Cardiac output (liter per minute) / heart rate (beats per minute)

If the calculation is based on echocardiography, the formula is as follows:

Stroke volume = end diastolic volume - end systolic volume

Stroke index is the stroke volume corrected for body surface area. Formula is as follows:

Stroke volume / body surface area (in m2)

Ejection fraction is the percentage of ventricular volume ejected during each systole. The formula is as follows:

Ejection fraction = stroke volume (cc per beat) / end diastolic volume (cc) × 100, expressed as percentage of end-diastolic volume

Compliance is the property of a material of undergoing elastic deformation and is equal to the reciprocal of stiffness.

Compliance is an important concept in human physiology, and it applies to the ventricles, the atria, as well as the pericardium, lungs, the pleura—all affected by changes in pressure and volume.

Using the left ventricle as an example, if the chamber dilates but diastolic pressure remains low, that means that the ventricle has increased its compliance (i.e., mitral regurgitation). The opposite is if the ventricular volume does not change much but its diastolic pressure increases, that is decreased compliance.

Fig. 1.2. Pressure (y-axis) versus volume (x-axis) illustrates compliance.

Peripheral vascular resistance (PVR) or total peripheral resistance (TPR) is the resistance offered to blood flow by the systemic vasculature.

The major regulator of vascular resistance is the vessel radius. Resistance is inversely proportional to the fourth power of the radius of vessels; therefore, small changes in diameter result in large increases or decreases in vascular resistance.

Regulation of vessel radius is a major factor in