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Patient-Centered Cardiovascular Diagnostics

Thomas Bartel, MD, PhD, Interventional Cardiologist, Flexdoc GmbH

Cardiovascular diagnostics can be coarsely divided in clinical assessment, electrocardiographic methods, laboratory diagnostics, imaging approaches and special invasive procedures. Some are considered screening tests, e.g. clinical examination, surface ECG and transthoracic echocardiography, which has widely replaced chest x-ray as a basal approach. Personalization of advanced diagnosis has an increasing role.

Clinical Assessment

Exploration of case history also known as anamnesis as well as clinical examination represent the classic first steps into any diagnosis. Examination starts with the vital signs also called ‘vitals’ usually collected by nursing staff include body temperature, respiration rate (rate of breathing) and pulse rate, which mostly but not always represents heart rate (HR). Blood pressure (BP) and oxygen saturation (SO2) are not considered vital signs but are often measured along with them. Clinical examination includes auscultation of heart, lung and vessels as well as qualitative and quantitative assessment of pulses, search for edema and other signs of congestion, skin color and some specific signs, e. g. clubbing of nails also called ‘hippocratic nails’ being indicative of chronic oxygen deficiency and often caused by congenital heart diseases. These findings are not trivial but reveal important information enabling subsequent set up of dedicated plans for stepwise laboratory and instrument-based cardiovascular diagnostics. Having said this, anamnesis and clinical examination can be considered crucial for patient-centricity of the whole diagnostic process in cardiology and angiology.  

Laboratory Diagnostics

In cardiovascular medicine, laboratory testing can be employed for direct diagnosis of particular pathology, e.g. troponin-I is increased if the heart muscle has been acutely damaged after myocardial infarction or myocarditis. Cardiac biomarkers, e.g. NT-pro-BNP, are sensitive and specific in congestive heart failure (CHF) and help estimating severity of the same. Other tests are routinely done for screening purposes and cardiovascular risk profiling, e.g. lipid panel, blood sugar, renal functional markers or blood uric acid level. Cardiovascular risk assessment has a lot of therapeutic and preventive implications as are changes in lifestyle or targeted medical therapy. Some screening tests are used to exclude particular organ dysfunction, which may interfere with the cardiovascular system, e.g. serum electrolytes and thyroid stimulating hormone may be indicative of adrenal or thyroid dysfunction, which can cause several cardiac symptoms up to life-threatening conditions.

Instrument-based Cardiovascular Diagnosis

A distinction is made between functional and morphological diagnostics. Electrocardiographic (ECG-based) as well as electrophysiological methods, exercise tests, hemodynamic testing and measurements fall under functional diagnostic approaches. Imaging techniques are predominantly used for morphological evaluation, although they are often combined with functional testing, e.g. echocardiography always includes qualitative and quantitative Doppler assessments, which enable physicians to draw conclusions about valvular dysfunction, intracardiac shunts as well as systolic and diastolic left ventricular function. All instrument-based procedures have to be performed in a strictly standardized way in order to ensure comparability and appropriateness. That is way personalization in medicine does not include this level.

ECG-based Diagnostic Approaches

Surface ECG is considered a mandatory screening test and does not require special indication. It shows various kinds of dysrhythmia, conduction abnormalities, signs of myocardial damage and ischemia (hypoxia of the myocardium). Even though some diagnoses can be directly made from surface ECG, e.g. conduction blocks, the method has two major limitations:

1. Many ECG abnormalities are nonspecific.
2. ECG just registers abnormalities occurring at a moment and at rest. Arrhythmias and other changes not occurring permanently or just under physical challenge remain undetected.

That is why, long-term ECG also known as Holter-ECG is much more sensitive in terms of arrhythmias occurring intermittently. Alternatively, long-term ECG registration can be provided by telemetry. Sometimes, implantable devices for long-term monitoring are used in order to detect arrhythmias which are experienced seldom but may explain symptoms like sudden loss of consciousness which is also called ‘syncope’. Ergometry includes ECG-registration at different stress levels and can be combined with various imaging techniques as are echocardiography, nuclear medicine imaging (nuclear stress test) and magnetic resonance imaging (MRI) in order to improve sensitivity and specificity in terms of myocardial ischemia, which is a typical dysfunctional result of coronary artery disease (CAD).

Cardiovascular Imaging

Echocardiography, vascular ultrasound, computed tomography (CT), and MRI reveal acquired and congenital morphological abnormalities of all cardiac and vascular structures, e.g. valvular or coronary calcification (Figure 1). These imaging modalities also enable measurement of dimensions, e.g. vessel diameters, cardiac chamber sizes and valve opening areas. They visualize and determine flow and flow velocities inside the heart and the vasculature. Important hemodynamic parameters, e.g. left ventricular ejection fraction (LVEF), pressure gradients across stenotic valves, pulmonary artery pressure, regurgitant orifice areas at leaking valves can be calculated or reliably estimated. Thus, these imaging approaches provide with a lot of functional parameters, too.

Ultrasound based methods, CT and MRI have their own sensitivity, specificity and accuracy in terms of detecting designated abnormalities and diseases. They entail different costs, e.g. personnel expenditures and costs for equipment. Transthoracic and transesophageal echocardiography (TTE and TEE) are provided by cardiology staff. MRI and CT are established in radiology and vascular ultrasound may be offered by angiology or radiology staff. TTE has replaced traditional chest x-ray as a first line approach in (Figure 1)

Figure 1: two cases of CAD with main stem stenosis (arrows) due to calcification of the central left coronary artery. By courtesy of G. Feuchtner, MD, PhD.
 
Cardiology. TEE, CT and MRI are more expensive and are therefore considered second line approaches, which require specific indication. For example, cardiac CT is indicated to show or exclude CAD and TEE is known to be very sensitive and specific for endocarditis (destructive bacterial infection of heart valves). With an increasing number of surgical and catheter-based therapies both techniques are also used as preoperative or periinterventional guiding tools. All imaging approaches have special features to be used for specific questions and tasks, e.g. three-dimensional TEE for post-interventional assessment of the mitral valve (Figure 2).

Figure 2: mitral valve after implantation of a MitraClip® device (arrows) for treatment of mitral valve insufficiency; left side – valve from above; right side – valve from below.

Beside specific indications and diagnostic questions, other criterions exist to choose the optimal diagnostic approach for an individual. Of course, guidelines and professional recommendations preset which imaging modality might be used for distinct scenarios. However, all approaches have downsides, e.g. CT entails radiation exposure and usually requires application of a contrast agent. Echocardiography does not require radiation exposure and ultrasonic contrast agents do not interfere with renal function. On the other hand, TEE is a semi-invasive approach and requires the patient to swallow a probe under mild sedation. Standard MRI may be contraindicated in patients with metallic implants or claustrophobia. That is why informed consent needs to be obtained from patients for all instrumental diagnostic modalities except for ECG approaches and TTE.

Beside modalities mentioned, there are other imaging approaches, which are established under nuclear medicine, e.g. single-photon-emission-tomography (SPECT) and positron-emission-tomography (PET), both of which use radioactive tracers. In cardiology, SPECT is performed as a stress test and shows myocardial perfusion. Baseline measurement is followed by another reading after physical of pharmacological stress. Perfusion defects at rest are indicative of myocardial scars after infarction whereas reversible perfusion defects under stress are indicative of ischemia due to coronary stenoses in patients with CAD. In contrast to SPECT, there are just a few and very specific indications for PET in cardiology, e.g. inflammatory spots inside the heart can be detected in endocarditis. Generally, SPECT and PET should just be employed if other approaches mentioned above do not provide with sufficient information.             

Other Non-invasive Testing

Diagnosis of heart failure (inability of the heart to pump sufficient amounts of blood) cannot be imagined without spiroergometry, which is a cardiopulmonary exercise test using respiratory gas exchange analysis for the assessment of functional capacity and prognosis of individuals with CHF. It can be beneficially used for follow-up, detection of poorest prognosis and optimal timing of heart transplantation. Together with heart failure biomarkers, spiroergometry helps a lot to guide any heart failure therapy throughout the whole spectrum of severity.

The tilt table test is another functional diagnostic approach, which is used to evaluate the cause of unexplained dizziness and fainting. The health care provider watches how heart and nervous system respond on changes in position of the human body. Several conditions potentially causing orthostatic hypotension include Parkinson’s disease, postural orthostatic tachycardia syndrome (POTS) and other neurally mediated conditions.      

Invasive Diagnostic Approaches

Invasive diagnostics require strong indication and informed consent by the patient. Coronary angiography (CAG) represents is the most frequently used diagnostic method in order to demonstrate coronary stenoses in detail. It can be combined with ad hoc therapy, namely percutaneous coronary intervention (PCI). However, CAG just shows coronary stenosis but does not provide with functional information. With other words, CAG is not very much specific regarding pathophysiological relevance of stenoses. As a result, moderate coronary stenoses require additional diagnostic efforts for final assessment and therapeutic decision-making. Intravascular ultrasound and measurement of fractional flow reserve (FFR) are considered much more specific and are often used to specify CAG findings prior to final assessment.

Comparable to the relation between CAG and PCI, there is a relation between intracardiac electrophysiological study (EPS) and electrophysiological ablation. EPS reveals pathophysiological background of arrhythmias and can be combined with ablation therapy as needed. The option of immediate therapy is advantageous for patients and may reduce costs, since double procedural preparation and aftercare are dropped. Consequently, invasive diagnosis might be favored if the need for therapeutic consequences is likely.       

Individualization vs. Standardization of Diagnostics

Guidelines released by European, American and other cardiac societies have been considered having force of law for decades. That widely led to strict standardization of diagnostics and subsequent therapy. However, pure standardization does not live up to current medical, ethical and social requirements anymore but represent a kind of averaging and does hardly cope with individual conditions. Guidelines and current recommendations are usually based on the outcome of trials, which explicitly disregard certain comorbidities, very old and young age, sometimes even gender and other individual conditions, e.g. genetic predispositions, history of cancer or mental illness. That is why, guidelines just provide medical community with a rough orientation regarding strategy of diagnostics, since each patient is unique. Optimal therapy requirs a personalized approach in terms of diagnosis as well as therapy rather than standardized but average handling. As an example, diagnostic methods based on radiation or radio contrast exposure might be avoided in cancer patients and individuals with renal failure. In contrast, diagnostic cascade should be tailored along individual needs and risks as well as the likelihood of positive findings. For example, if CAD needs to be excluded in an individual, cardiac CT is considered optimal, since it is very sensitive. In comparison, ergometric approaches followed by CAG are expedient in symptomatic or high-risk subjects in order to unequivocally prove CAD, since these tests are sensitive and very specific.

In summary, aspiration of patient-centered cardiovascular diagnostics requires conceptualization of a personalized diagnostic path along individual needs and health conditions. At this point, wheel turns full circle: just thorough exploration of case history and in-depth clinical assessment provide physicians with all information within and beyond cardiovascular medicine, which is needed for what can be called “patient-centricity”. Patient-centered diagnostics require more time, knowledge and personal engagement by physicians compared to standardized diagnostic paths, which just follow presets. Finally, it’s worth it to make these efforts because to current knowledge, it represents the best way to avoid misdiagnoses on the one hand and diagnostic overkill on the other hand. Patient-centered diagnosis can be considered the entrance into patient-centered care at all. It also helps to improve patient’s compliance and may counteract skyrocketing costs in healthcare.

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Author Bio

Thomas Bartel

Dr. Thomas Bartel is an interventional cardiologist with about 35 years of professional experience. He finished Charité Medical School in Berlin in 1987. He worked at different academic institutions in Germany, the United States, Austria and the United Arab Emirates. In that regard, he was confronted with a broad spectrum of healthcare conditions and systems.

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