Cardiology Diagnostics Part 1
Diagnostic Medicine I - Fall 2023
Prepared by: John Bowers, MPAS, PA-C
Objectives:
By the end of this class, you should be able to:
Understand the indications and/or contraindications (when
applicable) for use of cardiac catheterization, cardiac stress testing,
ESR/CRP, and cardiac “enzyme” testing.
Apply acquired knowledge to clinical or case scenarios and
appropriately order these diagnostic modalities.
Understand limitations to these diagnostic tests (if any) and any
available strategies to mitigate the effect of these limitations on
diagnosis of disease states.
Class Preview
This class will cover:
Cardiac Catheterization
Cardiac Enzymes
Stress Testing Basics
ESR/CRP and the role of these diagnostics in cardiac/riskfactor testing
Cardiac Enzyme
Testing
Troponin, CK-MB, etc.
To Start, Let’s Define
What We Are Looking for….
Identifying “ischemia” or “infarction” is the target of our
testing.
This occurs when any imbalance between the demand of oxygen
(and/or nutrients) outweighs the supply of those things.
This is the most common cause of cardiac injury.
Possible causes = vessel stenosis or occlusion, extreme exercise
when not conditioned, trauma, toxins, and/or certain infections
Cardiac Injury
Cardiac injury occurs when there is a disruption of the normal
cardiac myocyte membrane. This results in a loss of intracellular
contents into the into the extracellular space (think similar to RBC
cell lysis)
This leads to detectable levels of biologically active
proteins/enzymes such as troponin, creatine kinase (CK),
myoglobin in the blood stream.
Measuring these enzymes helps to indicate cardiac injury or
ischemia.
When do we use enzyme testing? –
Indications:
When assessing for measureable evidence of cardiac injury
(regardless of underlying reason).
Examples include:
MI/STEMI or NSTEMI, demand ischemia, myocarditis, etc.
Clinical Example
A 47 y/o male patient presents to the ER for c/o chest pain.
He reports the pain began 2hrs PTA. The pain radiates across
his chest from left side to R and is worse with prolonged
ambulation. The pain is occurring at rest or with activity.
The pain is described as dull, but occasionally sharp when at it’s
worst, rated 7/10 at worst. No hx of similar.
Vital signs only remarkable for elevated BP of 150/90. No recent
injury to explain pain otherwise.
No SOB, no leg swelling.
No cough, dyspnea, orthopnea.
History of tobacco use x 20 years (1 ppd)
What do you want to do?
About Cardiac Enzyme Testing
Also referred to as cardiac biomarker testing
These tests are indicative of myocardial injury
Myoglobin (MB),
Creatinine kinase (CK)
Creatinine kinase MB isoenzyme (CK–MB),
Cardiac troponins (troponin I or T)
Which of these are most specific to the myocardium?
CK-MB
Note: small amount found in other tissues
Cardiac troponins (more specific to myocardium than CK–MB)
Note: *Troponin I is more cardiac specific than troponin T
Cardiac Enzyme Timeline
Which biomarker peaks first?
First detected in bloodstream: Myoglobin (within 8 hours)
Which biomarker persists longest?
Last to clear bloodstream: Troponin(s)
Note: Recent research results have allowed us to understand that troponins should begin to
rise within 2- hours of acute-onset MI (previously thought 4 hours, at earliest). Conservative
approach is now 4 hours.
NSTEMI vs. STEMI: Classification
(i.e. Chest pain)
Following disruption of a plaque, patients
experience ischemic discomfort resulting from
reduced flow through an affected coronary
artery.
The flow reduction may be caused by a
completely occlusive thrombus (right) or
partial occlusion (left).
Patients with ischemic discomfort may present
w/ or w/o ST elevation. Of patients with STelevation, the majority (wide red arrow)
ultimately develop a Q wave on the ECG (Qw
MI), while a minority (thin red arrow) do not
develop Q wave. (NQMI). These are old terms,
not used today.
Patients who present without ST elevation are
suffering from either unstable angina or a nonST elevation MI (NSTEMI) (right green arrow), a
distinction that is made based on the presence
or absence of a serum cardiac biomarker
In addition to plaque rupture or acute obstruction –
what are other causes of cardiac troponin elevation?
Cardiac tissue damage due to “demand ischemia”
Tachyarrhythmias, profoundly anemic state with high cardiac demand,
significant hypo/hyper-tension, HF, LVH, severe AS, PE, coronary
vasculitis, coronary vasospasm, sepsis, acute respiratory failure
Cardiac tissue damage not due to ischemia
Cardiac contusion, recent cardiac surgery or ablation therapy,
myocarditis, Takotsubo cardiomyopathy (apical ballooning), cardiotoxic
agents, frequent or recent defibrillator shocks (appropriate or inappropriate)
Extra-cardiac causes of elevated troponin?
Cerebrovascular Stroke
àThe most likely explanation in this setting is an imbalance of the autonomic
nervous system, with resulting excess of sympathetic activity and increased
catecholamine effect on the myocardial cells
Test Selection:
Creatine kinase (CK) and it’s MB isoenzyme (CK-MB) were
previously the most commonly used serologic tests for the
diagnosis of MI prior to the widespread use of troponin(s).
We can now diagnose “microinfarctions” by highly sensitive
troponin assays.
These highly sensitive assays may be positive even when CK-MB levels may be
in the normal reference range.
As such, cardiac troponins are the preferred biomarkers for
diagnosis and prognosis of MI in many clinical settings.
**It is often unnecessary to obtain both types of testing (i.e.
troponin and CK-MB at the same time).
Summary (cont’d)
Myoglobin and lactate dehydrogenase should no longer be used
for the evaluation of patients with ACS and/or acute MI.
At one time, myoglobin’s early appearance in serum was postulated
to be a useful adjunct to troponin or CK-MB for the early
diagnosis of MI
à But…clinical data suggests that cardiac troponin outperforms
each of these tests in almost every way.
Reference Ranges for Commonly
Used Cardiac Enzymes
Troponin I – Reference range = <0.35 ng/mL (may vary by institution
and method tested)
Troponin T – Reference range = <0.2 mcg/L (may vary by institution and
method tested)
CK-MB – Reference range = <9.0 ng/mL
If you see any elevation of any of these above the reference range or
upward trending you should consider myocardial ischemia
*(Don’t forget to consider other diagnoses or reasons for elevated cardiac enzymes)
Clinical Utility of Troponin – As used
with the “HEART SCORE”
*MACE = Major adverse cardiac event
Clinical Utility of Troponin (cont’d)
Using “serial” troponins (defined as
measuring troponin in 2, 3, or 4 hour
increments after an initial measure)
helps reassure the provider and patient
that a troponin is not trending upward.
What if pt walks in now?
Troponin likely will not show up in blood stream until 4
hrs after onset of infarction, thus why this is important.
Troponin: clinical application
Results from the “MIDAS” studyAn analysis was conducted of 1005 participants in the diagnosis of acute coronary
syndromes
MIDAS was a prospective observational cohort of Emergency Department patients enrolled
from 18 US sites with symptoms suggestive of acute coronary syndrome (ACS)
The North American Chest Pain Rule (NACPR) = a patient is considered low-risk if they have no high risk criteria.
Cardiac Stress Testing
The “let’s see what happens” test
Intro
Cardiac stress testing:
An important diagnostic and prognostic tool used to evaluate
patients for suspected heart disease.
Both exercise and pharmacologic types of stress testing assesses
cardiac function by:
Increasing the myocardial oxygen demand
And thus, helps to reveal inadequate oxygen supply (hypo-perfusion)
from diseased or narrowed coronary arteries
Particularly helpful in any patient w/ symptoms that do not occur at rest
(i.e. stable angina)
Indications for Stress Testing
Evaluation of:
Exertional chest pain or symptoms suggestive of angina in a patient
with moderate or high level of suspicion of CAD
***Pre-test history & risk assessment is key
Assess significance or progression of known coronary artery disease
Determine a patient’s general exercise capacity
Valvular disease (to determine effect on exercise capacity)
Select arrhythmias (to determine their effect on myocardial perfusion)
To evaluate new-onset heart failure or cardiomyopathy (why?)
Why = To evaluate for ischemic heart disease as a cause for that new heart
failure (or a cardiomyopathy of uncertain etiology), assuming that coronary
angiography has not already been planned or performed.
Other Indications:
Patients with chronic left ventricular dysfunction and coronary artery
disease who are candidates for revascularization (via catheterization) (why?)
Stress testing PLUS imaging can identify areas of myocardial ischemia and regions of
viable myocardium
This information is helpful in the planning of revascularization
Acute chest pain of undetermined etiology
Pain must resolve prior to stress testing
Otherwise, you could incite a true MI
(never send a patient with active chest pain to a stress test)
Select high-risk patients undergoing non-cardiac surgery
Why?
Preoperative evaluation of patients prior to elective surgery, can help
identify patients with active cardiac conditions that should undergo further
evaluation and treatment prior to scheduled surgery
Absolute Contraindications to Stress Testing
Active chest pain concerning for ACS/MI,
Unstable angina or known MI recently (<72 hrs)
Uncontrolled arrhythmias with hemodynamic compromise
Don’t make the mistake of sending a hypotensive patient to get a stress test! K, Thanks!
Acute decompensated heart failure
Known CHF, with acute worsening recently (of any etiology)
Active or acute endocarditis, myocarditis, or pericarditis
Acute aortic dissection
Symptomatic severe valvular stenosis
Acute pulmonary embolism, pulmonary infarction, or DVT
Physical disability that precludes safe or adequate testing
Methods of Testing
The two most common methods of exercise stress testing are:
1. ECG-based only = Exercise stress testing while connected to a
live-recording ECG machine (to look for active changes with exertion)
2. Imaging based = Exercise stress (or by pharmacologic stress) with
ECG, followed by imaging.
Imaging is usually either ECHO or radionuclide testing
Patient Monitoring During Testing
Regardless of testing type, monitor the patient carefully by:
Asking the patient to report subjective symptoms of chest
pain, SOB or dyspnea, light-headedness/near-syncope, etc.
These should be reason to stop the test
Physical findings should also be assessed during testing such as
peripheral cyanosis (i.e. signs of poor perfusion), hypotension,
excessive increase or decrease in HR, pulmonary rales (signs of
HF)
Differences in Modalities?
ECG-based exercise stress testing is the simplest measure to evaluate for
exertion-induced myocardial ischemia as evidences by changes on the
ECG during testing.
Imaging-based stress testing (whether exercise-based or pharmacologic
stress-induced can help to more specifically isolate where a flowlimiting lesion is within the coronary anatomy.
Imaging-based modality is preferred in these patient groups:
Those undergoing pharmacologic stress testing (due to lower sensitivity
compared to exercise)
Prior revascularization (due to abnormal coronary anatomy)
Significantly abnormal resting ECG
Patients using Digoxin
Comparing types:
ECG-Based
Imaging-Based
Commonly first-line in those who
can exercise and have routine ECG
findings at rest
Better in select patients
(mentioned on prior slide)
(i.e. baseline ECG is not complex)
Less expensive than imaging-based
Less helpful to specifically locate a
coronary artery lesion
May be converted to imaging-based
during test
Particularly if elicited ECG
abnormalities are non-specific
Better to isolate area of a
lesion/flow limitation
May be the preliminary test if
ECG portion was felt to be
inaccurate, complex, or nonspecific in its findings
Increasing in preferred
prevalence
SUMMARY: EXERCISE ECG ALONE OR
AS A COMBO MODALITY?
Exercise stress testing with electrocardiographic (ECG)
monitoring should be the initial test of choice for the majority
of patients who can exercise and who have an ECG which can
be adequately interpreted.
Exercise stress testing with imaging has certain advantages over
the standard exercise testing, but there is insufficient evidence
at this time to recommend exercise stress testing with imaging
in all patients.
Special Stress Imaging
Stress Echocardiography
Provides real-time cardiac functional assessment in several possible
situations:
At rest,
During or after- dynamic exercise,
Or during pharmacologic stress testing
Helps to determine if there is need for a valvular repair /replacement.
Particularly those pts with asymptomatic significant aortic stenosis (such
as in congenital biscupid aortic valve)
Why?
To determine prognosis and/or severity of disease
Other indications:
Stress ECHO may also be performed to other valvular
diseases such as:
Severe mitral stenosis without symptoms,
Moderate mitral stenosis with symptoms,
Severe mitral or aortic regurgitation (when left ventricular size
and function do not meet surgical criteria)
Pharmacologic-based Stress Test
Often indicated when a patient has a limitation which causes them to be unable
to complete the normal treadmill exercise portion (either inadequately or cannot
complete at all)
-Examples: due to handicap, due to injury, poor exercise tolerance, neurologic
deficit, severe arthritis, etc.
Chemicals Used (2 Main Types)
1.) Ionotropes/Chronotropes:
Dobutamine (a synthetic catecholamine)
Stimulates beta1-adrenergic receptors à increasing the heart rate
(chronotropic effect) & myocardial contractility (inotropic effect).
2.) Vasodilators:
Including: Adenosine*; dipyridamole; and the selective A2A
receptor agonists including: regadenoson, binodenoson, and
apadenoson
Theophylline and caffeine should be withheld 48 and 12 hrs before
vasodilator stress resting, respectively, since these agents can decrease
the effectiveness of vasodilators.
Contraindications 1
For Inotrope/Chronotrope (Dobutamine) Stress Testing:
Sustained or frequent ventricular arrhythmias and atrial fibrillation
with rapid ventricular response (RVR)
Why: (may precipitate a worse or life threatening, arrhythmia)
Recent myocardial infarction (within one to three days) or unstable
angina /complicated ACS
Why: (contraindicated for all stress modalities)
*Aortic dissection
Why: (increased rate/pressure may increase risk of rupture)
Moderate to severe systemic hypertension
I.e. resting systolic blood pressure >180 mmHg
Contraindications 2
For Vasodilator Stress Testing:
Significant active bronchospastic airway disease
Why: (these drugs may stimulate bronchospasm)
Significant hypotension
Why: (these drugs will further transiently lower blood pressure)
Sick sinus syndrome (SSS) and/or high-degree AV block without a
functioning pacemaker
Why: (these drugs may worsen preexisting conduction disease
and/or incite 3rd degree block)
Unstable or complicated acute coronary syndrome
Why: (an increased risk for acute ischemic events is present with all
stress modalities)
BREAK TIME
Cardiac Catheterization
The gold standard test for true/thorough
assessment of the coronary arteries.
Spooky History of Catheterization:
Fact or Fiction?
In 1929 Werner Forssman, a resident surgeon at Eberswalde in
Germany, inserted a urologic catheter into his right atrium
from a left antecubital vein cutdown he had performed on
himself using a mirror.
After walking downstairs to the radiology suite, the position of
the catheter tip was verified by a roentgenogram (now known as xray).
This was the beginning of cardiac catheterization (i.e. the insertion
and passage of small plastic catheters into arteries, veins, the heart,
and other vascular structures for a variety of indications).
Catheterization: How is it performed
First – consent must be obtained. The procedure must be explained,
including risks, if applicable (i.e. non-emergent situation)
Emergent cath’s may not require consent (i.e. a life threatening condition)
Second – a site of insertion of the catheter must be determined
Femoral artery (most common currently) –vs.– . Radial artery (gaining
popularity due to less complications)
Then, a metal “guide wire” is passed into the artery and used to allow
softer, more flexible plastic catheters to be introduced into appropriate
areas of the heart.
Once the catheter is in place (inside the heart or coronary artery of
choice) pressures are measured and/or dye is injected (angiography) to
allow the clinician to see filling defects, structural abnormalities, or
atypical flow characteristics.
How is it performed? (cont’d)
If you click the link below you will see how the two methods of
catheter insertion compare:
https://youtu.be/vuHHjIRswDE?t=1m45s
Videos:
Click this link to see how cardiac catheterization can detect
coronary artery abnormalities
General animated instructional video (no sound)
Click the link below to watch an actual case with live dye
injection:
https://youtu.be/JeH4zPzQgRc
After clicking, forward to 1:16 once you have listened to the first 20
seconds (indication for procedure is announced).
Right vs. Left Heart Cath
Right heart catheterization is no longer a routine part of general
diagnostic cardiac catheterization when evaluating the coronary
arteries
It is mainly used to evaluate the venous system / pulmonary arteries
Indicated to evaluate:
Unexplained dyspnea, valvular heart disease of the R side to determine
extent of disease, pericardial disease, right and/or left ventricular
dysfunction, congenital heart disease, and suspected intracardiac shunts.
Right vs. Left Heart Cath
Left heart catheterization is the gold standard method used to
evaluate coronary vasculature
As well as:
left ventricular & left atrial filling pressures, and occasionally, the
aortic valve
When speaking of coronary artery disease and assessment as a
whole, left heart catheterization is the gold standard.
Right vs. Left Cath: Pathway
Specific Indications for Left
Heart Catheterization
Cardiac catheterization is used to assess for and/or diagnose:
*Atherosclerotic coronary artery disease
Also: severe pericardial disease, cardiomyopathy, assess for causes of
heart failure, and can be used in identifying valvular or congenital
heart abnormalities.
Please note: Ultrasound is increasingly being used to assess for and diagnose
valvular heart disease. As such, in some cases that means catheterization may
no longer be required
Catheterization helps to determine extent and severity of cardiac
dz & determine if medical, surgical, or other interventions are
needed
(i.e. medication management vs. bypass graft vs. stenting)
General Info About Cath
In general, cardiac catheterization is an elective diagnostic
procedure
(It has the potential for therapeutic intervention to address any
issues discovered during the procedure)
For emergent indications, particularly if the patient is unstable from
a suspected cardiac cause such as acute MI, catheterization should
be completed as soon as possible.
Absolute Contraindications
Generally speaking, there are no absolute contraindications for
an emergently-indicated heart cath procedure
Must simply do Risk vs. Benefit
Note:
You must have a well-prepared facility and trained provider to
perform cardiac catheterization
Not all hospitals have the tools or trained providers to perform catheterization
Relative Contraindications
Relative contraindications to cardiac catheterization include:
Fever
Significant/profound anemia
Electrolyte imbalance (especially hypokalemia predisposing to
arrhythmias)
Renal failure (why?)
Pregnancy (why?)
Uncontrolled bleeding as in supratherapeutic anticoagulated state
Acute GI bleed
Or other systemic illnesses requiring emergent stabilization
PCI vs. CABG
Percutaneous coronary intervention (PCI) refers to:
Non-stent procedures on one or more coronary arteries (such as
balloon angioplasty)
OR stent interventions
There are a variety of types of intra-coronary stents.
In general, stents are characterized according to:
Type of material, thickness of struts, and as to whether or not they are
capable of eluting medication(s) for local delivery in the artery
Stenting is generally indicated when a vessel reaches >/=70%
diameter* stenosis.
*Under that value, it is at the discretion of the performing provider.
PCI vs. CABG
When a patient has significant multi-vessel disease, Coronary
Artery Bypass Graft (CABG) is typically warranted.
The percentages of each vessel may vary, so it is up to the
performing provider to determine need for CABG
There may be patient-specific and case-specific factors weighing in…
CABG – Terminology Review
Heart Catheterization Complications
The incidence of major risks of stroke, death, and myocardial
infarction is approximately 0.1%
The minor risks of vascular injury, allergic reaction, bleeding,
hematoma, and infection range from 0.04% to 5% and should
be discussed.
Pain post procedure in area of catheter insertion may be
common, particularly within 48 hours of the procedure.
High risk populations:
Certain patient groups are at higher risk for complications (for a
variety of reasons):
Acute myocardial infarction (*), Advanced age (>75 y), Aortic
aneurysm, Aortic stenosis, Congestive heart failure, Diabetes,
Extensive three-vessel coronary artery disease, Left ventricular
dysfunction (left ventricular ejection fraction <35%), Obesity, prior
stroke, Renal insufficiency, left main coronary artery stenosis,
Unstable angina (w/ plaque that may rupture)
Other Considerations
The following constitute groups who may need special
consideration in testing:
Patients with diabetes mellitus (Insulin use? Hypoglycemia risk?)
For diabetic patients, long-acting or NPH insulin dosing should be
adjusted overnight due to fasting state!
Normal morning dose of insulin could cause hypoglycemia during
procedure.
Renal insufficiency (due to contrast dye use)
Prior allergy to iodinated contrast media
Prophylactic measures exist to reduce risks to these pts
Allergic reactions to contrast agents occur in <5% of cases
Use of ESR/CRP Labs
The “not-so-specific” labs
ESR = erythrocyte sedimentation rate
CRP = serum C-reactive protein concentration.
ESR/CRP Overview:
ESR/CRP are both non-specific biomarkers of inflammation.
Both cannot tell you WHERE the inflammation is – just that it
“is” or “is not” present overall
(Thus, the test is sensitive, not specific)
ESR value changes slowly as patient's condition worsens or
improves
Whereas CRP changes more rapidly, and may better reflect
acute disease/problems
Timeframe comparison
Reference Ranges:
ESR= Normal for Males—1 to 17 mm/h; females—0 to 25
mm/h.
CRP= Normal < 0.8 mg/dL
Cardiac-Specific Implications?
Since pericarditis is an inflammatory disease, laboratory signs of
inflammation are commonly observed in pts with acute
pericarditis.
This may include elevations in the white blood cell count, ESR
and/or CRP
While elevation in these markers supports the diagnosis, they are
neither sensitive nor specific for acute pericarditis.
But, may be helpful in confirming a diagnosis in which you are
suspecting…
What other diagnostic abnormalities might you see to suggest
pericarditis?
Cautious Use
ESR/CRP may also be elevated in autoimmune, rheumatologic
diseases, diseases of chronic inflammation as well as postsurgical states.
In these conditions, ESR/CRP may be of little use
That said, be mindful that inflammatory processes are
important contributors to vessel disease and vulnerability of an
atherosclerotic lesion to rupture or erosion.
Summary - CRP
CRP is the most extensively studied biomarker of inflammation
in cardiovascular disease (CVD).
Increased serum CRP correlates with traditional cardiovascular
risk factors.
But, it should NEVER be used alone to determine cardiovascular
risk
It may reflect contributions of these risk factors toward vascular
inflammation.
Chronically elevated serum CRP has been associated with a
higher risk of future cardiovascular events.
*However, the value of this information for individual risk
stratification and direction of therapy continues to be debated.
Summary (cont’d)
For the determination of cardiovascular risk, low-, average-,
and high-risk values of CRP are defined as <1, 1 to 3, and >3
mg/L, respectively.
These values can be used in certain risk-level populations to
modify current therapies
(may suggest need to add a statin, lifestyle modifications, etc.)
*Values >10 mg/L should prompt concern of a specific
source of infection or inflammation and likely necessitates
repeat measurement of hs-CRP in 10-21 days.
(highly-sensitive) = hs
That’s all!
Questions?
ewald@musc.edu