Established Cardiovascular Disease: Commonly Missed Diagnoses and How to Manage Them

Why Missed Diagnoses Matter in Established CVD

Patients with a prior MI, stroke, or peripheral arterial disease already carry a high baseline MACE risk. Each undiagnosed comorbidity stacked on top of that baseline compounds event rates in a way that is rarely linear. A single missed diagnosis of heart failure with preserved ejection fraction, for example, can double hospitalization risk without triggering any of the standard secondary-prevention alarms that a cardiologist monitors.

The Diagnostic Inertia Problem

Diagnostic inertia in established CVD is well documented. The 2023 ACC/AHA Guideline on Chronic Coronary Disease notes that patients with known atherosclerotic cardiovascular disease (ASCVD) are often under-screened for comorbid conditions that share overlapping symptoms with their primary diagnosis [1]. Dyspnea gets attributed to known coronary disease. Leg pain gets attributed to deconditioning. Daytime fatigue gets attributed to beta-blocker therapy. Each of these symptom attributions forecloses the diagnostic workup that would catch the actual driver.

Why the Stakes Are Higher Than in Primary Prevention

Secondary prevention patients are, by definition, people who have already survived a major event. The SELECT trial enrolled 17,604 adults with overweight or obesity and established CVD but without diabetes, and even in that treated population receiving standard secondary-prevention therapy, the placebo arm experienced a 6.5% rate of three-point MACE over a median of 39.8 months [2]. That background event rate underscores how much residual risk remains even when guideline-directed medical therapy is in place.

Heart Failure With Preserved Ejection Fraction (HFpEF)

HFpEF is the most systematically under-diagnosed condition in patients with established CVD. Up to 50% of all heart failure cases involve a preserved ejection fraction, yet the diagnosis is frequently missed because the ejection fraction looks normal on echocardiography and the presentation is dominated by symptoms the clinician already attributes to the underlying coronary disease [3].

Recognizing the Clinical Picture

The cardinal symptoms, exertional dyspnea, orthopnea, and peripheral edema, overlap completely with decompensated coronary disease and with the side-effect profiles of calcium channel blockers and nitrates. The H2FPEF score, validated in the European Heart Journal, uses BMI, hypertension, atrial fibrillation, pulmonary hypertension on echo, age over 60, and elevated filling pressures to stratify probability without requiring invasive hemodynamics [4]. A score of 6 or higher carries a greater than 90% probability of HFpEF.

Diagnostic Workup

Brain natriuretic peptide (BNP) or NT-proBNP should be ordered in any established CVD patient with unexplained dyspnea. The 2022 AHA/ACC/HFSA Heart Failure Guideline assigns a Class IIa recommendation to diastolic stress testing when resting echo is inconclusive [5]. Cardiac MRI adds tissue characterization that echocardiography cannot provide and should be considered when infiltrative cardiomyopathy (amyloid, hemochromatosis) is on the differential.

Management Implications

SGLT2 inhibitors have changed the HFpEF management picture substantially. EMPEROR-Preserved (N=5,988) showed empagliflozin 10 mg reduced the composite of CV death or HF hospitalization by 21% vs. Placebo (HR 0.79, 95% CI 0.69 to 0.90, P<0.001) in patients with HFpEF, regardless of diabetes status [6]. Clinicians managing established CVD patients with HFpEF should add an SGLT2 inhibitor to the regimen even when diabetes is absent.

Peripheral Arterial Disease (PAD)

PAD is present in a substantial minority of patients with coronary artery disease, but most clinical encounters focus exclusively on the coronary tree. The ABI (ankle-brachial index) is not routinely measured at cardiology follow-up visits despite a Class I recommendation for its use in patients with suspected lower-extremity PAD from the 2016 AHA/ACC Lower Extremity PAD Guideline [7].

The Asymptomatic Majority

Up to 70% of PAD cases present without classic claudication. Patients report vague leg fatigue, slow wound healing, or nothing at all. In the PARTNERS study, only 11.7% of PAD patients in primary care had a prior diagnosis, despite an ABI-confirmed prevalence of 29% in patients over age 70 or over age 50 with diabetes or smoking history [8]. The same pattern almost certainly applies to the established CVD population.

Screening Protocol

An ABI below 0.90 is diagnostic for PAD. Testing takes under 10 minutes and requires only a handheld Doppler and a blood pressure cuff. Any established CVD patient with diabetes, a smoking history, or unexplained lower-extremity symptoms should have an ABI measured. Duplex ultrasound follows a low ABI to map stenosis location and severity before referral for revascularization assessment.

Treatment Overlap and Drug Choices

PAD and CAD share an antiplatelet backbone, but drug selection matters. COMPASS (N=27,395) showed rivaroxaban 2.5 mg twice daily plus aspirin 100 mg reduced the composite of CV death, MI, and stroke by 24% vs. Aspirin alone in stable atherosclerotic vascular disease, with the benefit particularly pronounced in PAD patients [9]. Cilostazol 100 mg twice daily improves walking distance in claudication and carries a Class I recommendation in the 2016 PAD guideline [7].

Obstructive Sleep Apnea (OSA)

OSA affects an estimated 40 to 80% of patients with established coronary artery disease, yet a formal polysomnography diagnosis is documented in only a small fraction of cardiology charts [10]. The mechanism is straightforward: recurrent nocturnal hypoxia drives sympathetic surges, endothelial dysfunction, and systemic inflammation, each of which accelerates atherosclerosis progression.

Why It Goes Undetected

Cardiologists ask about dyspnea. They less often ask about snoring, witnessed apneas, or morning headaches. Patients with established CVD are frequently on multiple sedating medications, which blunt the subjective sense of sleep disruption and reduce the reported Epworth Sleepiness Scale score. A normal ESS score does not exclude OSA in this population.

Screening and Diagnosis

The STOP-BANG questionnaire (Snoring, Tired, Observed apnea, high blood Pressure, BMI >35, Age >50, Neck >40 cm, male Gender) has a sensitivity above 90% for moderate-to-severe OSA at a score of 3 or higher [10]. Any established CVD patient scoring 3 or higher on STOP-BANG should be referred for home sleep apnea testing or in-lab polysomnography.

CPAP and Cardiovascular Outcomes

The ISAACC trial (N=2,717) found that CPAP did not reduce MACE in a population of patients with acute coronary syndrome and OSA over a median follow-up of 3.35 years [11]. Interpretation requires context: adherence averaged only 2.8 hours per night, which falls below the 4-hour threshold considered therapeutic. Observational data from high-adherence populations continue to show CV event reduction, and CPAP remains standard of care for symptomatic OSA regardless of the ISAACC null result.

Type 2 Diabetes and Prediabetes as Missed Concurrent Diagnoses

A fasting glucose or HbA1c is not always repeated at cardiology visits, even though the ADA recommends annual HbA1c in all patients with established ASCVD given the high co-prevalence of dysglycemia [12]. The SELECT trial excluded patients with diabetes, yet 40% of enrolled patients had prediabetes at baseline. That group still derived a significant MACE reduction from semaglutide, pointing to metabolic drivers that operate independently of a formal diabetes diagnosis.

Screening Gap in Practice

The 2019 ESC/EASD Guidelines on Diabetes and Cardiovascular Disease recommend an oral glucose tolerance test (OGTT) when fasting glucose alone does not clarify glycemic status in patients with established CVD [13]. The OGTT detects post-load hyperglycemia that a fasting glucose misses entirely. Approximately 35% of patients with known CAD have undiagnosed type 2 diabetes or impaired glucose tolerance on formal OGTT testing.

GLP-1 Receptor Agonists After the SELECT Trial

The SELECT trial (N=17,604, median follow-up 39.8 months) showed semaglutide 2.4 mg subcutaneously once weekly reduced three-point MACE by 20% vs. Placebo (HR 0.80, 95% CI 0.72 to 0.90, P<0.001) in adults with BMI >27 and established CVD but no diabetes [2]. The FDA approved Wegovy (semaglutide 2.4 mg) for cardiovascular risk reduction in adults with established CVD and BMI ≥27 in March 2024 [14].

The practical framework for GLP-1 use in established CVD now depends on three variables: BMI threshold (≥27), diabetes status (absent, given SELECT population), and current MACE risk (prior MI, stroke, or symptomatic CAD confirmed). All three should be charted before initiation. Contraindications include a personal or family history of medullary thyroid carcinoma or MEN2A/2B syndrome.

Chronic Kidney Disease as a Cardiovascular Risk Multiplier

CKD stage 3 or above (eGFR <60 mL/min/1.73 m²) is present in roughly 30 to 40% of patients with established CVD, yet a significant proportion of these patients are not formally coded with CKD in their problem lists [15]. This matters for drug dosing, contrast nephropathy risk, and eligibility for SGLT2 inhibitors and newer non-steroidal mineralocorticoid receptor antagonists.

DAPA-CKD and FIDELIO-DKD Findings

DAPA-CKD (N=4,304) showed dapagliflozin 10 mg reduced the composite of sustained decline in eGFR of 50% or more, end-stage kidney disease, or renal or CV death by 39% vs. Placebo (HR 0.61, P<0.001) in patients with CKD regardless of diabetes status [16]. FIDELIO-DKD (N=5,674) showed finerenone 10 to 20 mg reduced a composite kidney endpoint by 18% and a composite CV endpoint by 14% vs. Placebo in patients with CKD and type 2 diabetes [17]. Both drugs are now guideline-supported in patients with CKD and established CVD when the overlapping indication is recognized.

Atrial Fibrillation Detected Late or After the Fact

Paroxysmal atrial fibrillation is frequently asymptomatic, particularly in patients already on rate-controlling agents prescribed for coronary disease. The 2023 ACC/AHA Guideline on Chronic Coronary Disease recommends rhythm monitoring with extended ambulatory ECG (14 to 30 days) in patients with unexplained palpitations, dyspnea, or cryptogenic stroke [1]. A 30-day patch monitor detects paroxysmal AF in roughly 12% of patients with a recent cryptogenic stroke who had a negative 24-hour Holter [18].

Anticoagulation Decision After AF Detection

When AF is confirmed in an established CVD patient already on dual antiplatelet therapy, the triple-therapy decision is one of the highest-stakes choices in outpatient cardiology. The AUGUSTUS trial (N=4,614) showed apixaban reduced bleeding vs. Vitamin K antagonists in AF patients with acute coronary syndrome or PCI, without increasing ischemic events, supporting a strategy of apixaban plus a P2Y12 inhibitor (dropping aspirin after the early post-PCI window) in most patients [19].

Depression and Cardiac Rehabilitation Non-Completion

Depression affects roughly 20% of post-MI patients and independently predicts recurrent MACE with a hazard ratio of approximately 1.8 after adjustment for traditional risk factors [20]. Cardiac rehabilitation programs that address both physical reconditioning and psychosocial support reduce mortality by approximately 20 to 26% based on a 2016 Cochrane meta-analysis of 63 trials (N=14,486) [21]. Despite this, cardiac rehabilitation completion rates in the United States remain below 25% of eligible patients, and formal depression screening is absent from many cardiology follow-up protocols.

Screening Tools

The PHQ-9 takes under 3 minutes to administer. A score of 10 or higher warrants formal psychiatric evaluation or initiation of pharmacotherapy. SSRIs, particularly sertraline and escitalopram, have the most safety data in post-MI patients; the SADHART trial (N=369) showed sertraline was safe with respect to cardiac events and improved depression scores vs. Placebo over 24 weeks [20].

Lipid Abnormalities Beyond LDL-C

Standard lipid panels in established CVD focus on LDL-C, but two additional markers, lipoprotein(a) and triglyceride-rich remnant particles, are missed by the basic panel and carry independent MACE risk that statin therapy does not fully address.

Lp(a) Screening

Lipoprotein(a) above 50 mg/dL (or 125 nmol/L) is present in approximately 20% of the general population and confers an approximately 1.5-fold increase in MACE risk independent of LDL-C [22]. The 2022 ACC Expert Consensus Decision Pathway recommends measuring Lp(a) at least once in all patients with ASCVD to identify candidates for emerging therapies (PCSK9 inhibitors partially lower Lp(a); dedicated Lp(a)-lowering agents including pelacarsen and olpasiran are in Phase 3 trials) [22].

Hypertriglyceridemia and Remnant Cholesterol

Fasting triglycerides above 200 mg/dL identify patients with elevated remnant cholesterol. REDUCE-IT (N=8,179) showed icosapentaenoic acid (Vascepa) 4 g/day reduced MACE by 25% vs. Placebo in patients with established CVD or high-risk diabetes and fasting triglycerides 135 to 499 mg/dL on statin therapy [23]. This benefit was not replicated in STRENGTH (N=13,078) using a different omega-3 formulation (EPA plus DHA), suggesting the benefit is specific to pure EPA [23].

Putting It Together: A Systematic Missed-Diagnosis Checklist

Every established CVD patient at any follow-up visit should prompt a brief mental checklist covering eight domains:

1. HFpEF: BNP or NT-proBNP ordered if dyspnea is unexplained. Diastolic stress echo if BNP is borderline.
2. PAD: ABI measured if diabetes, smoking history, or leg symptoms are present.
3. OSA: STOP-BANG administered. Score ≥3 triggers sleep study referral.
4. Dysglycemia: HbA1c annually; OGTT if HbA1c is 5.7 to 6.4% and clinical suspicion is high.
5. CKD: eGFR and urine albumin-to-creatinine ratio at least annually.
6. Paroxysmal AF: 14 to 30-day ambulatory ECG for unexplained palpitations or cryptogenic stroke.
7. Depression: PHQ-9 at every post-MI or post-stroke visit through 12 months.
8. Lp(a) and triglycerides: Lp(a) once per patient lifetime; fasting triglycerides annually in patients on statin therapy.