DIAGNOSTIC APPROACH TO HEART FAILURE CASE FOR DISCUSSION: ‘LEFT VS. RIGHT’
PAUL R. FORFIA, M.D

Heart failure may be defined as a syndrome of effort intolerance, often with salt/water retention, that is related to underlying cardiac dysfunction. The HF syndrome may arise from dysfunction of the left side of the heart, right side of the heart, or both. For the purpose of this discussion, we will define left heart failure (LHF) as the HF syndrome that arises from dysfunction of the left ventricle or left-sided valvular lesions, and right heart failure (RHF) as that arising from dysfunction of the right ventricle or right sided valvular lesions. Therefore, in RHF, the lesion should reside either proximal to or within the lung. So-called ‘biventricular failure’ is rooted in left sided cause, and will thus be treated as LHF.

We will focus the discussion on the practical and clinically relevant matter of recognizing the differences in the HF presentation between those presenting with LHF in the setting of a normal LV ejection fraction (so-called ‘diastolic’ HF or ‘HF with a preserved LV ejection fraction’ or HFpEF) versus those RHF related to pulmonary hypertension resulting exclusively from pulmonary vascular disease (RHFPAH). The reason being, patients with HFpEF and RHFPAH will present with HF, a normal LVEF, and in most cases, evidence of pulmonary hypertension on their initial echo-Doppler examination. Thus, on first glance, patients with HFpEF and RHFPAH can ‘look the same’, however, on further inspection, these patients have a markedly different phenotype. We will review the salient differences between these two populations with the intent of aiding in the rapid clinical distinction of these two populations.

The differences between HFpEF and RHFPAH begin with basic epidemiologic characteristics. Robbins et al showed that patients with HFpEF are on average, more obese (BMI 36.8) than those with PAH (BMI 29.2), and that patients with >=2 features of the metabolic syndrome are far more likely to have HFpEF than PAH (odds ratio 30.7) (1). Patients with HFpEF are also more likely to have atrial fibrillation, coronary artery disease, systemic hypertension and chronic kidney disease than patients with PAH (1, 2). Table 1 highlights some of the common distinguishing features between patients with HFpEF and RHFPAH. Although dyspnea is nearly universal in all forms of PH, exertional angina and syncope are characteristic in RHFPAH. Exertional angina and syncope are distinctly uncommon in HFpEF, where symptoms of pulmonary congestion predominate. It is common to assume RHF is present in a patient whom is breathless and presents with marked volume overload and peripheral edema, especially if rales are absent on pulmonary auscultation. In this authors’ experience, this assumption is very often incorrect, and is reflected by data showing that most patients with chronic LHF do not have rales on examination, while only 37% of patients with PAH will have peripheral edema on their initial presentation (3,4).

In a recent referral cohort of PH patients, a normal systolic blood pressure response to Valsalva maneuver (VM) was typical of the RHFPAH population, with an average pulmonary artery wedge pressure (PAWP) of 12 mmHg with an average PVR of 8.1 mmHg/L/min (2). Subjects with a sustained elevation in the systolic blood pressure to VM (so-called ‘square wave’ ) had HFpEF, with an average PAWP of 23 mmHg. The BP response to VM was 87% accurate at detecting a PAWP > 15 mmHg, and outperformed Doppler and B-type natriutetic peptide analysis in making this distinction (2).

Normal LVEF and the presence of pulmonary hypertension aside, a more thorough analysis of the echo-Doppler exam will often reveal striking phenotypic differences the HFpEF and PAH populations. On 2-D examination, patients with HFpEF most often have left ventricular hypertrophy and left atrial enlargement, while patients with PAH will nearly always possess the triad of RV enlargement, RV dysfunction, and septal bowing (5,6). On Doppler examination, patients with HFpEF typically possess either Grade II (pseudonormal) or Grade III (restrictive) diastolic dysfunction; in contrast, RHFPAH is typically characterized by either Grade I diastolic dysfunction owed to impaired passive filling of the LV induced by RV enlargement and septal bowing, or normal diastolic function (5-7). Arkles et al recently showed that a normal configuration of the RVOTDoppler signal (no Doppler ‘notching’) was associated with PH related to an increased PAWP and a normal PVR with an odds ratio of 33:1; a ‘notched’ RVOTDoppler pattern was associated with a PVR > 3 mmHg/l/min with an odds ratio of 29:1 (8). In this study, 100% of the patients with a new diagnosis of PAH had evidence of ‘notching’ of the RVOTDoppler signal.

Definitive hemodynamic assessment requires right heart catheterization. The HFpEF patient will have a relatively normal or mildly increased PVR (typically < 5 mmHg/L/min) and markedly increased PAWP, whereas the RHFPAH patient will typically have a markedly increased PVR (mean 8-10 mmHg/L/min) and a normal PAWP or equivalent (i.e. LV end-diastolic pressure). Of note, the PAWP measurement is prone to error in patients with PH, which can lead to misdiagnosis and therapy. The PAWP is commonly underestimated in the obese patient due to failure to measure the PAWP at end-expiration-this can lead to a false diagnosis of PAH. The PAWP can also be overestimated by recording a partial occlusion pressure, leading to a false diagnosis of PVH, and a missed diagnosis of PAH (7). Both of these pitfalls can be easily managed by using correct PAWP assessment technique, however some centers prefer to obtain an LV end-diastolic pressure as the preferred method of left heart filling pressure assessment.

In summary, clinical differentiation of a patient with HFpEF versus another with RHFPAH requires an integration of salient clinical and echo-Doppler features of the patient presentation, along with invasive hemodynamic assessment performed by an experienced operator. The noninvasive and invasive patient assessment should be viewed as complimentary approaches that will most often lead to the correct diagnosis, which is especially important as their diagnostic and treatment strategies differ considerably.

Definition of abbreviations: PND- paroxysmal nocturnal dyspnea; sBP-systolic blood pressure; VM-Valsalva maneuver LVH-left ventricular hypertrophy; LAE-left atrial enlargement; RVH-right ventricular hypertrophy; RAE-right atrial enlargement; P2-pulmonic closure sound; MR-mitral regurgitation; MS-mitral stenosis; TR-tricuspid regurgitation; RVOTDoppler-pulsed wave Doppler signal obtained from right ventricular outflow tract; PASP-pulmonary artery systolic pressure.

References
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