Ischemic Heart Disease Study Notes (CAD/CHD/CVD, Angina, PT Role, and Exercise Testing)

CAD, CHD, and CVD: Terminology and Clinical Context

Cardiovascular disease (CVD) is the broadest umbrella term for diseases affecting the heart and blood vessels, including coronary heart disease, stroke, and peripheral arterial disease. Within CVD, heart disease refers to conditions that primarily affect the heart’s structure and function, such as valvular disease, arrhythmias, and cardiomyopathies. Coronary artery disease (CAD) refers specifically to narrowing or blockage of the coronary arteries due to atherosclerosis, while coronary heart disease (CHD) is a broader term that includes CAD and its sequelae, such as myocardial infarction (MI) and heart failure. In clinical practice, CAD is the more commonly used term for documentation and guidelines.

CAD results from plaque buildup in the coronary arteries that progressively restricts blood flow to the heart muscle. The clinical course often progresses from stable angina—ischemia during exertion—to acute coronary syndromes (ACS) such as MI or sudden occlusion with permanent myocardial damage. Notably, MI can occur without preceding stable angina when a previously non-significant plaque ruptures suddenly, triggering thrombus formation. This pathway underlines the variable and sometimes abrupt nature of ischemic events.

Ischemia arises when myocardial oxygen demand exceeds supply, typically due to impaired coronary blood flow. Ischemia primarily affects the subendocardium—the innermost myocardial layer—because it is farthest from the coronary arteries and most vulnerable to reduced perfusion. The clinical implication is that symptoms and risk of damage correlate with how supply-demand balance shifts during activity or stress.

Angina and Myocardial Ischemia: Pathophysiology

Angina is the clinical manifestation of an oxygen supply/demand imbalance in the myocardium. Exercise or other stress increases myocardial oxygen demand; when supply cannot meet this demand, ischemia develops. The pattern of ischemia and angina can vary by individual and by the type of ischemic insult.

There are several forms of angina. Stable angina is the most common and is provoked by exertion due to a fixed coronary obstruction. It is typically relieved by rest or nitroglycerin, which lowers myocardial oxygen demand through systemic vasodilation rather than directly improving coronary perfusion. Unstable angina is a progression from stable CAD that can occur at rest; it does not follow a predictable pattern and signals potential transition to ACS. It requires urgent medical attention due to the risk of complete occlusion.

Variant (Prinzmetal) angina is caused by transient coronary vasospasm rather than fixed atherosclerotic narrowing. It can occur even with minimal coronary disease and often responds to vasodilators such as calcium channel blockers and nitroglycerin.

Angina pain is typically referred, as afferent cardiac sensory fibers (T1–T5) converge with other chest and upper body sensory pathways. This explains pain radiation to the chest, left arm, shoulder, neck, jaw, and throat, though presentations can vary widely. Gender differences are pronounced: men more often report classic substernal chest pain with radiation to the left arm or neck, accompanied by exertional discomfort and diaphoresis; women more commonly report neck, jaw, back discomfort, nausea, dyspnea, and unusual fatigue, which can delay recognition. Silent ischemia is also possible—ischemia without typical chest pain—especially in individuals with diabetes, the elderly, or post-transplant patients, often due to autonomic neuropathy affecting sensory feedback. Silent ischemia is usually detected via ST-segment changes during stress testing rather than patient-reported symptoms.

Recognizing and Managing Suspected Cardiac Ischemia During Activity: Practical PT Considerations

If a patient presents with undifferentiated symptoms that may relate to cardiac ischemia, the initial step is to place the patient in a resting position to see if reducing cardiac demand alleviates symptoms. Immediate relief with rest or nitroglycerin (if prescribed) supports a possible stable ischemic pattern. Risk-factor assessment is essential: hypertension, hyperlipidemia, diabetes, smoking, obesity, physical inactivity, and other known atherosclerotic factors increase the likelihood that symptoms are cardiac-related.

It is crucial to differentiate cardiac ischemia from musculoskeletal chest pain. Musculoskeletal etiologies may respond differently to movement or deep breathing; chest palpation or observing symptom changes with arm movements can aid differentiation. For example, a young adult with recent rib fractures using axillary crutches might have chest pain during use that fits a general angina description but is musculoskeletal rather than cardiac in origin due to absence of atherosclerotic risk factors.

In contrast, an older adult with hypertension, type 2 diabetes, a long smoking history, and exertional chest pain that relieves with rest would heighten suspicion for true ischemia and prompt further cardiac evaluation and possible referral.

Once ischemia is suspected, objective testing is needed to confirm diagnosis and assess cardiovascular function. Invasive options include coronary angiography with cardiac catheterization; noninvasive options include exercise testing and other modalities to assess ischemia and functional capacity. PTs should understand these tests to guide safety, activity recommendations, and collaboration with physicians. While exercise testing is within the PT scope in many settings, performing physician-ordered tests—especially those evaluating the extent of cardiovascular disease—often requires additional training beyond entry-level PT education. Thus, generally, entry-level PTs refer for these tests rather than performing them themselves.

Four types of testing commonly described in the literature are exercise tolerance testing (ETT or stress testing), cardiopulmonary exercise testing (CPET), and pharmacologic stress testing. ETT evaluates the heart’s response to exertion by monitoring vitals, ECG changes, and symptoms, typically continuing to symptom limitation or volitional fatigue. CPET provides a more comprehensive physiological assessment by measuring oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilatory efficiency (VE/VO2) to differentiate cardiac from pulmonary limitations and to provide precise VO2 max measurement. Pharmacologic stress testing uses agents such as dobutamine (to increase heart rate and contractility, mimicking exercise) or adenosine (to induce coronary vasodilation and reveal perfusion deficits) when physical exercise is not feasible. Dobutamine stress echocardiography detects wall-motion abnormalities, while vasodilator nuclear stress testing assesses perfusion using imaging.

For PTs, understanding these testing modalities enhances collaboration with physicians and informs rehabilitation decisions. Test results help tailor interventions, establish safe exercise intensities, and optimize conditioning programs for those recovering from ischemic events or managing chronic heart disease. In many real-world settings, PTs may not have access to formal testing and must rely on real-time cardiovascular monitoring during activity—observing vitals, symptoms, and tolerance to exercise to detect abnormal responses and ensure safety. Key monitoring parameters include heart rate (to detect excessive rises or blunted responses), blood pressure (expect a gradual systolic rise; a drop may indicate hemodynamic instability), respiratory rate, and oxygen saturation. PTs should remain vigilant for signs of ischemia, arrhythmias (e.g., irregular pulse, palpitations, dizziness), and reduced exercise tolerance. Absence of ECG access in some settings necessitates reliance on palpation and patient reporting to detect irregularities.

When formal testing is not feasible or available, submaximal exercise testing serves as a practical alternative. Submaximal protocols involve graded walking or cycling to approximately 85% of age-predicted maximal heart rate to assess cardiovascular response, establish safe intensity limits, and gauge readiness for progression. Importantly, the angina threshold—the point at which exertion provokes ischemia—serves as a critical guide for prescribing exercise intensity.

The Angina Threshold: Definition and Clinical Utility

The angina threshold is defined as the specific point during exertion where myocardial ischemia first occurs due to an imbalance between oxygen supply and demand. Identifying this threshold enables precise exercise prescription to maximize cardiovascular benefits while minimizing risk. In practice, clinicians monitor heart rate, perceived exertion, and work rate (METs or watts) to determine the threshold and tailor exercise prescriptions.

Submaximal testing procedures commonly track:

Heart rate (HR) at the onset of ischemic symptoms or angina
Rating of perceived exertion (RPE)
Work rate, expressed as METs or watts

A practical approach is to determine the ischemic threshold during a graded test and then set a safety ceiling slightly below that threshold to avoid provoking ischemia. The transcript provides concrete examples:

Example 1: If a patient experiences angina at a heart rate of 100 bpm with an RPE of 13 and at 4 METs, the exercise program should be planned to stay just below these values to maximize benefit while avoiding ischemia.
Example 2 (ischemic threshold for a different patient): If angina occurs at a heart rate of 150 bpm, the ceiling might be set at 140 bpm (a 10 bpm buffer) to account for day-to-day variability in heart rate, oxygen demand, and external stressors. This buffer helps prevent inadvertent triggering of ischemia while still providing a meaningful cardiovascular stimulus.

It is acknowledged that experienced clinicians in tightly controlled environments with continuous ECG monitoring may occasionally allow exercise near or at the threshold, and in some cases with mild angina as part of ischemic preconditioning to improve tolerance. However, this approach requires specialized training and risk management beyond typical entry-level practice.

The angina threshold concept is foundational to designing safe and effective exercise programs for patients with ischemic heart disease. By staying below the threshold, patients can gain cardiovascular benefits while reducing the risk of symptomatic ischemia and adverse events. Over time, regular training can shift the angina threshold upward, meaning the same workload elicits less ischemia and higher functional capacity.

Exercise Training and Ischemic Heart Disease: Mechanisms and Real-World Outcomes

Exercise training improves the capacity of individuals with stable ischemic heart disease to perform physical activity. A conceptual comparison illustrates the effect of training on myocardial oxygen consumption relative to workload. In a hypothetical scenario, two individuals—one without ischemic heart disease and one with CAD—perform the same workload (e.g., 3 METs). The non-ischemic individual can sustain this workload without ischemia, whereas the CAD patient may cross the ischemic threshold due to insufficient supply. After a period of structured exercise training, the CAD patient can perform the same workload but consume less myocardial oxygen, avoiding ischemia. This improvement is attributed to multiple adaptations, including improved endothelial function, better autonomic control, enhanced skeletal muscle efficiency, more favorable oxygen use, and angiogenesis (growth of new blood vessels). These adaptations collectively enhance myocardial perfusion and functional capacity.

From a practical standpoint, PTs can use this information to educate patients about the benefits of consistent exercise and to motivate adherence to lifestyle changes. By communicating the potential for safer, more capable activity with training, therapists can support long-term behavioral change, which is often challenging for patients dealing with chronic heart disease.

In the broader educational pathway, the course notes indicate that ECG interpretation and telemetry analysis will be covered in subsequent sessions, aiding clinicians in recognizing ischemia on monitoring data. The next units will delve into telemetry-based ECG analysis to identify ischemic patterns and arrhythmias, further supporting safe clinical practice.

Key Formulas and Quantitative References (Quick Reference)

1 MET corresponds to a specific oxygen uptake: 1 ext{ MET} = 3.5\ rac{\text{mL}}{\text{kg} \cdot \text{min}}
Maximum heart rate estimation: HR_{ ext{max}} = 220 - \text{age}
Target HR for submaximal training: HR{ ext{target}} = 0.85 imes HR{ ext{max}}
Ischemia threshold concept: the threshold is the exercise intensity at which ischemia first occurs; in practice, prescribe exercise just below this value (e.g., ceiling = threshold - 10 bpm) to account for daily variability: ext{Ceiling} = HR_{ ext{ischemia}} - 10\ ext{bpm}
CPET outputs include quantitative measures such as VO2 peak (maximal oxygen uptake), VO2max, and ventilatory efficiency metrics such as the slope of VE vs. VCO2, often expressed as VE/VCO_2 slope.
Pharmacologic stress testing uses agents like dobutamine and adenosine to mimic exercise or induce vasodilation for perfusion assessment; imaging modalities include dobutamine stress echocardiography and vasodilator nuclear stress testing.

Practical Implications for Clinical Practice

PTs should be able to recognize and differentiate cardiac versus musculoskeletal chest pain and know when to refer for advanced cardiac evaluation.
When imaging or physiologic testing is not available, submaximal testing with careful observation can provide meaningful data to guide safe exercise prescriptions.
The angina threshold concept provides a robust framework for setting exercise intensity that balances therapeutic cardiovascular stimulation with risk minimization.
Exercise training exerts beneficial effects on endothelial function, autonomic balance, skeletal muscle efficiency, and myocardial oxygen utilization, contributing to improved functional capacity and quality of life for patients with CAD.
Ethical and safety considerations include recognizing the limits of PT scope of practice, avoiding overly aggressive testing in uncontrolled settings, and ensuring timely referral when ischemia is suspected or when symptoms are unresolved.

Conclusions and Look Ahead

This unit connected cardiovascular disease terminology to clinical progression, clarified the types of angina, and emphasized the PT role in recognizing ischemia, initiating appropriate referrals, and guiding safe exercise prescription. The angina threshold emerged as a central concept for tailoring exercise programs to individual patients. The course will continue with ECG interpretation and telemetry analysis in upcoming sessions to further enhance the practical skillset required for monitoring and managing patients with ischemic heart disease during activity.