Quantification of vessel-specific coronary perfusion territories using minimum-cost path assignment and computed tomography angiography: Validation in a swine model

Improved diagnostic accuracy of vessel-specific myocardial ischemia by coronary computed tomography angiography (CCTA)

BACKGROUND

Discrepancies between stenosis severity assessed at coronary computed tomography angiography (CCTA) and ischemia might depend on vessel type. Coronary plaque features are associated with ischemia. Thus, we evaluated the vessel-specific correlation of CCTA-derived diameter stenosis (DS) and invasive fractional flow reserve (FFR) and explored whether integrating morphological plaque features stratified by vessel might increase the predictive yield in identifying vessel-specific ischemia.

METHODS

Observational cohort study including patients undergoing CCTA for suspected coronary artery disease, with at least one vessel with DS ​≥ ​50 ​% at CCTA, undergoing invasive coronary angiography and FFR. Plaque analysis was performed using validated semi-automated software. Coronary vessels were stratified in left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA). Per vessel independent predictors of ischemia among CCTA-derived anatomical and morphologic plaque features were tested at univariable and multivariable logistic regression analysis. The best cut-off to predict ischemia was determined by Youden's index. Ischemia was defined by FFR≤0.80.

RESULTS

The study population consisted of 192 patients, of whom 224 vessels (61 ​% LAD, 19 ​% LCX, 20 ​% RCA) had lesions with DS ​≥ ​50 ​% interrogated by FFR. Despite similar DS, the rate of FFR≤0.80 was higher in the LAD compared to LCX and RCA (67.2 ​% vs 43.2 ​% and 44.2 ​%, respectively, p ​= ​0.018). A significant correlation between DS and FFR was observed only in LAD (p ​= ​0.003). At multivariable analysis stratified by vessel, the vessel-specific independent predictors of positive FFR were percent atheroma volume (threshold>17 ​%) for LAD, non-calcified plaque volume (threshold >130 ​mm3) for LCX, and lumen volume (threshold <844 ​mm3) for RCA. Integrating DS and vessel-specific morphological plaque features significantly increased the predictive yield for ischemia compared to DS alone (AUC ranging from 0.51 to 0.63 to 0.76-0.80).

CONCLUSIONS

Integrating DS and vessel-specific morphological plaque features significantly increased the predictive yield for vessel-specific ischemia compared to DS alone, potentially improving patients' referral to the catheterization laboratory.

Absolute coronary flow and microvascular resistance before and after transcatheter aortic valve implantation

BACKGROUND

Severe aortic stenosis (AS) is associated with left ventricular (LV) remodelling, likely causing alterations in coronary blood flow and microvascular resistance.

AIMS

We aimed to evaluate changes in absolute coronary flow and microvascular resistance in patients with AS undergoing transcatheter aortic valve implantation (TAVI).

METHODS

Consecutive patients with AS undergoing TAVI with non-obstructive coronary artery disease in the left anterior descending artery (LAD) were included. Absolute coronary flow (Q) and microvascular resistance (Rμ) were measured in the LAD using continuous intracoronary thermodilution at rest and during hyperaemia before and after TAVI, and at 6-month follow-up. Total myocardial mass and LAD-specific mass were quantified by echocardiography and cardiac computed tomography. Regional myocardial perfusion (QN) was calculated by dividing absolute flow by the subtended myocardial mass.

RESULTS

In 51 patients, Q and R were measured at rest and during hyperaemia before and after TAVI; in 20 (39%) patients, measurements were also obtained 6 months after TAVI. No changes occurred in resting and hyperaemic flow and resistance before and after TAVI nor after 6 months. However, at 6-month follow-up, a notable reverse LV remodelling resulted in a significant increase in hyperaemic perfusion (QN,hyper: 0.86 [interquartile range {IQR} 0.691.06] vs 1.20 [IQR 0.99-1.32] mL/min/g; p=0.008; pre-TAVI and follow-up, respectively) but not in resting perfusion (QN,rest: 0.34 [IQR 0.30-0.48] vs 0.47 [IQR 0.36-0.67] mL/min/g; p=0.06).

CONCLUSIONS

Immediately after TAVI, no changes occurred in absolute coronary flow or coronary flow reserve. Over time, the remodelling of the left ventricle is associated with increased hyperaemic perfusion.

Reproducibility of a single-volume dynamic CT myocardial blood flow measurement technique: validation in a swine model

BACKGROUND

We prospectively assessed the reproducibility of a novel low-dose single-volume dynamic computed tomography (CT) myocardial blood flow measurement technique.

METHODS

Thirty-four pairs of measurements were made under rest and stress conditions in 13 swine (54.3 ± 12.3 kg). One or two acquisition pairs were acquired in each animal with a 10-min delay between each pair. Contrast (370 mgI/mL; 0.5 mL/kg) and a diluted contrast/saline chaser (0.5 mL/kg; 30:70 contrast/saline) were injected peripherally at 5 mL/s, followed by bolus tracking and acquisition of a single volume scan (100 kVp; 200 mA) with a 320-slice CT scanner. Bolus tracking and single volume scan data were used to derive perfusion in mL/min/g using a first-pass analysis model; the coronary perfusion territories of the left anterior descending (LAD), left circumflex (LCx), and right coronary artery (RCA) were automatically assigned using a previously validated minimum-cost path technique. The reproducibility of CT myocardial perfusion measurement within the LAD, LCx, RCA, and the whole myocardium was assessed via regression analysis. The average CT dose index (CTDI) of perfusion measurement was recorded.

RESULTS

The repeated first (Pmyo1) and second (Pmyo2) single-volume CT perfusion measurements were related by Pmyo2 = 1.01Pmyo1 - 0.03(ρ = 0.96; RMSE = 0.08 mL/min/g; RMSE = 0.07 mL/min/g) for the whole myocardium, and by Preg2 = 0.86Preg1 + 0.13(ρ = 0.87; RMSE = 0.31 mL/min/g; RMSE = 0.29 mL/min/g) for the LAD, LCx, and RCA perfusion territories. The average CTDI of the single-volume CT perfusion measurement was 10.5 mGy.

CONCLUSION

The single-volume CT blood flow measurement technique provides reproducible low-dose myocardial perfusion measurement using only bolus tracking data and a single whole-heart volume scan.

RELEVANCE STATEMENT

The single-volume CT blood flow measurement technique is a noninvasive tool that reproducibly measures myocardial perfusion and provides coronary CT angiograms, allowing for simultaneous anatomic-physiologic assessment of myocardial ischemia.

KEY POINTS

A low-dose single-volume dynamic CT myocardial blood flow measurement technique is reproducible. Motion misregistration artifacts are eliminated using a single-volume CT perfusion technique. This technique enables combined anatomic-physiologic assessment of coronary artery disease.

Coronary Microvascular Dysfunction in Patients With Heart Failure: Characterization of Patterns in HFrEF Versus HFpEF

BACKGROUND

Coronary microvascular dysfunction (CMD) is involved in heart failure (HF) onset and progression, independently of HF phenotype and obstructive coronary artery disease. Invasive assessment of CMD might provide insights into phenotyping and prognosis of patients with HF. We aimed to assess absolute coronary flow, absolute microvascular resistance, myocardial perfusion, coronary flow reserve, and microvascular resistance reserve in patients with HF with preserved ejection fraction and HF with reduced ejection fraction (HFrEF).

METHODS

Single-center, prospective study of 56 consecutive patients with de novo HF with nonobstructive coronary artery disease divided into HF with preserved ejection fraction (n=21) and HFrEF (n=35). CMD was invasively assessed by continuous intracoronary thermodilution and defined as coronary flow reserve <2.5. Left ventricular and left anterior descending artery-related myocardial mass was quantified by echocardiography and coronary computed tomography angiography. Myocardial perfusion (mL/min per g) was calculated as the ratio between absolute coronary flow and left anterior descending artery-related mass.

RESULTS

Patients with HFrEF showed a higher left ventricular and left anterior descending artery-related myocardial mass compared with HF with preserved ejection fraction (P<0.010). Overall, 52% of the study population had CMD, with a similar prevalence between the 2 groups. In HFrEF, CMD was characterized by lower absolute microvascular resistance and higher absolute coronary flow at rest (functional CMD; P=0.002). CMD was an independent predictor of a lower rate of left ventricular reverse remodeling at follow-up. In patients with HF with preserved ejection fraction, CMD was mainly due to higher absolute microvascular resistance and lower absolute coronary flow during hyperemia (structural CMD; P≤0.030).

CONCLUSIONS

Continuous intracoronary thermodilution allows the definition and characterization of patterns with distinct CMD in patients with HF and could identify patients with HFrEF with a higher rate of left ventricular reverse remodeling at follow-up.

Low-dose quantitative CT myocardial flow measurement using a single volume scan: phantom and animal validation

Purpose

To validate a low-dose, single-volume quantitative CT myocardial flow technique in a cardiovascular flow phantom and a swine animal model of coronary artery disease.

Approach

A cardiovascular flow phantom was imaged dynamically over different flow rates (0.97 to 2.45    mL / min / g ) using 15 mL of contrast per injection. Six swine (37 ± 8    kg ) were also imaged dynamically, with different left anterior descending coronary artery balloon stenoses assessed under intracoronary adenosine stress, using 1    mL / kg of contrast per injection. The resulting images were used to simulate dynamic bolus tracking and peak volume scan acquisition. After which, first-pass single-compartment modeling was performed to derive quantitative flow, where the pre-contrast myocardial attenuation was assumed to be spatially uniform. The accuracy of CT flow was then assessed versus ultrasound and microsphere flow in the phantom and animal models, respectively, using regression analysis.

Results

Single-volume quantitative CT flow measurements in the phantom (Q CT _ PHANTOM ) were related to reference ultrasound flow measurements (Q US ) by Q CT _ PHANTOM = 1.04 Q US - 0.1 (Pearson's r = 0.98 ; RMSE = 0.09    mL / min / g ). In the animal model (Q CT _ ANIMAL ), they were related to reference microsphere flow measurements (Q MICRO ) by Q CT _ ANIMAL = 1.00 Q MICRO - 0.05 (Pearson's r = 0.96 ; RMSE = 0.48    mL / min / g ). The effective dose per CT measurement was 1.21 mSv.

Conclusions

The single-volume quantitative CT flow technique only requires bolus tracking data, spatially uniform pre-contrast myocardial attenuation, and a single volume scan acquired near the peak aortic enhancement for accurate, low-dose, myocardial flow measurement (in mL/min/g) under rest and adenosine stress conditions.

Tissue-growth-based synthetic tree generation and perfusion simulation

Biological tissues receive oxygen and nutrients from blood vessels by developing an indispensable supply and demand relationship with the blood vessels. We implemented a synthetic tree generation algorithm by considering the interactions between the tissues and blood vessels. We first segment major arteries using medical image data and synthetic trees are generated originating from these segmented arteries. They grow into extensive networks of small vessels to fill the supplied tissues and satisfy the metabolic demand of them. Further, the algorithm is optimized to be executed in parallel without affecting the generated tree volumes. The generated vascular trees are used to simulate blood perfusion in the tissues by performing multiscale blood flow simulations. One-dimensional blood flow equations were used to solve for blood flow and pressure in the generated vascular trees and Darcy flow equations were solved for blood perfusion in the tissues using a porous model assumption. Both equations are coupled at terminal segments explicitly. The proposed methods were applied to idealized models with different tree resolutions and metabolic demands for validation. The methods demonstrated that realistic synthetic trees were generated with significantly less computational expense compared to that of a constrained constructive optimization method. The methods were then applied to cerebrovascular arteries supplying a human brain and coronary arteries supplying the left and right ventricles to demonstrate the capabilities of the proposed methods. The proposed methods can be utilized to quantify tissue perfusion and predict areas prone to ischemia in patient-specific geometries.

Absolute coronary flow and microvascular resistance reserve in patients with severe aortic stenosis

BACKGROUND

Development of left ventricle (LV) hypertrophy in aortic stenosis (AS) is accompanied by adaptive coronary flow regulation. We aimed to assess absolute coronary flow, microvascular resistance, coronary flow reverse (CFR) and microvascular resistance reserve (MRR) in patients with and without AS.

METHODS

Absolute coronary flow and microvascular resistance were measured by continuous thermodilution in 29 patients with AS and 29 controls, without AS, matched for age, gender, diabetes and functional severity of epicardial coronary lesions. Myocardial work, total myocardial mass and left anterior descending artery (LAD)-specific mass were quantified by echocardiography and cardiac-CT.

RESULTS

Patients with AS presented a significantly positive LV remodelling with lower global longitudinal strain and global work efficacy compared with controls. Total LV myocardial mass and LAD-specific myocardial mass were significantly higher in patients with AS (p=0.001). Compared with matched controls, absolute resting flow in the LAD was significantly higher in the AS cohort (p=0.009), resulting into lower CFR and MRR in the AS cohort compared with controls (p<0.005 for both). No differences were found in hyperaemic flow and resting and hyperaemic resistances. Hyperaemic myocardial perfusion (calculated as the ratio between the absolute coronary flow subtended to the LAD, expressed in mL/min/g), but not resting, was significantly lower in the AS group (p=0.035).

CONCLUSIONS

In patients with severe AS and non-obstructive coronary artery disease, with the progression of LV hypertrophy, the compensatory mechanism of increased resting flow maintains adequate perfusion at rest, but not during hyperaemia. As a consequence, both CFR and MRR are significantly impaired.

Dynamic CT myocardial perfusion without image registration

The aim of this study was to validate a motion-immune (MI) solution to dynamic CT myocardial perfusion measurement, in the presence of motion without image registration. The MI perfusion technique was retrospectively validated in six swine (37.3 ± 7.5 kg) with a motion-susceptible (MS) perfusion technique performed for comparison. In each swine, varying severities of stenoses were generated in the left anterior descending (LAD) coronary artery using a balloon under intracoronary adenosine stress, followed by contrast-enhanced imaging with 20 consecutive volume scans per stenosis. Two volume scans were then systematically selected from each acquisition for both MI and MS perfusion measurement, where the resulting LAD and left circumflex (LCx) measurements were compared to reference microsphere perfusion measurements using regression and diagnostic performance analysis. The MI (P_MI) and microsphere (P_MICRO) perfusion measurements were related through regression by P_MI = 0.98 P_MICRO + 0.03 (r = 0.97), while the MS (P_MS) and microsphere (P_MICRO) perfusion measurements were related by P_MS = 0.62 P_MICRO + 0.15 (r = 0.89). The accuracy of the MI and MS techniques in detecting functionally significant stenosis was 93% and 84%, respectively. The motion-immune (MI) perfusion technique provides accurate myocardial perfusion measurement in the presence of motion without image registration.

Blood flow modeling reveals improved collateral artery performance during the regenerative period in mammalian hearts

Collateral arteries bridge opposing artery branches, forming a natural bypass that can deliver blood flow downstream of an occlusion. Inducing coronary collateral arteries could treat cardiac ischemia, but more knowledge on their developmental mechanisms and functional capabilities is required. Here we used whole-organ imaging and three-dimensional computational fluid dynamics modeling to define spatial architecture and predict blood flow through collaterals in neonate and adult mouse hearts. Neonate collaterals were more numerous, larger in diameter and more effective at restoring blood flow. Decreased blood flow restoration in adults arose because during postnatal growth coronary arteries expanded by adding branches rather than increasing diameters, altering pressure distributions. In humans, adult hearts with total coronary occlusions averaged 2 large collaterals, with predicted moderate function, while normal fetal hearts showed over 40 collaterals, likely too small to be functionally relevant. Thus, we quantify the functional impact of collateral arteries during heart regeneration and repair-a critical step toward realizing their therapeutic potential.

CCTA-derived strain analysis in detection of regional myocardial dysfunction in coronary artery disease patients with preserved left ventricular ejection fraction: A feasibility study

OBJECTIVES

To evaluate the feasibility of using coronary computed tomography angiography (CCTA)-derived strain to detect regional myocardial dysfunction in coronary artery disease (CAD) patients with normal left ventricular ejection fraction (LVEF).

METHODS

A total of 1,580 segments from 101 patients who underwent stressed CT myocardial perfusion imaging (CT-MPI) and CCTA were retrospectively enrolled in this study. The CT-derived global and segmental strain values were evaluated using the feature tracking technique. Segments with myocardial blood flow (MBF) < 125 ml/min/100 ml and 95 ml/min/100 ml were categorized as ischemic and infarcted, respectively.

RESULTS

Segmental radial strain (SRS) and segmental circumferential strain (SCS) in the abnormal segments (including all segments with MBF < 125 ml/min/100 ml) were significantly lower than those in the normal segments (14.81±8.65% vs 17.17±9.13%, p < 0.001; -10.21±5.79% vs -11.86±4.52%, p < 0.001, respectively). SRS and SCS values in infarcted segments were significantly impaired compared with the ischemic segments (12.43±8.03% vs. 15.32±8.71%, p = 0.038; -7.72±5.91% vs. -10.67±5.66%, p = 0.010, respectively). The AUCs for SRS and SCS in detecting infarcted segments were 0.622 and 0.698, respectively (p < 0.05).

CONCLUSIONS

It is feasible for using CCTA-derived strain parameters to detect regional myocardial dysfunction in CAD patients with preserved LVEF. Segmental radial and circumferential strain have the potential ability to distinguish myocardial ischemia from infarction, and normal from ischemic myocardium.

Combining perfusion and angiography with a low-dose cardiac CT technique: a preliminary investigation in a swine model

Morphological and physiological assessment of coronary artery disease (CAD) is necessary for proper stratification of CAD risk. The objective was to evaluate a low-dose cardiac CT technique that combines morphological and physiological assessment of CAD. The low-dose technique was evaluated in twelve swine, where three of the twelve had coronary balloon stenosis. The technique consisted of rest perfusion measurement combined with angiography followed by stress perfusion measurement, where the ratio of stress to rest was used to derive coronary flow reserve (CFR). The technique only required two volume scans for perfusion measurement in mL/min/g; hence, four volume scans were acquired in total; two for rest with angiography and two for stress. All rest, stress, and CFR measurements were compared to a previously validated reference technique that employed 20 consecutive volume scans for rest perfusion measurement combined with angiography, and stress perfusion measurement, respectively. The 32 cm diameter volumetric CT dose index (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{CTDI}}_{\text{vol}}^{32}$$\end{document}CTDIvol32) and size-specific dose estimate (SSDE) of the low-dose technique were also recorded. All low-dose perfusion measurements (P_LOW) in mL/min/g were related to reference perfusion measurements (P_REF) through regression by P_LOW = 1.04 P_REF − 0.08 (r = 0.94, RMSE = 0.32 mL/min/g). The \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{CTDI}}_{\text{vol}}^{32}$$\end{document}CTDIvol32 and SSDE of the low-dose cardiac CT technique were 8.05 mGy and 12.80 mGy respectively, corresponding to an estimated effective dose and size-specific effective dose of 1.8 and 2.87 mSv, respectively. Combined morphological and physiological assessment of coronary artery disease is feasible using a low-dose cardiac CT technique.

Vessel-specific coronary perfusion territories using a CT angiogram with a minimum cost path technique and its direct comparison to the American Heart Association 17-segment model

OBJECTIVES

This study compared the accuracy of an automated, vessel-specific minimum cost path (MCP) myocardial perfusion territory assignment technique as compared with the standard American Heart Association 17-segment (AHA) model.

METHODS

Six swine (42 ± 9 kg) were used to evaluate the accuracy of the MCP technique and the AHA method. In each swine, a dynamic acquisition, comprised of twenty consecutive whole heart volume scans, was acquired with a computed tomography scanner, following peripheral injection of contrast material. From this acquisition, MCP and AHA perfusion territories were determined, for the left (LCA) and right (RCA) coronary arteries. Each animal underwent additional dynamic acquisitions, consisting of twenty consecutive volume scans, following direct intracoronary contrast injection into the LCA or RCA. These images were used as the reference standard (REF) LCA and RCA perfusion territories. The MCP and AHA techniques' perfusion territories were then quantitatively compared with the REF perfusion territories.

RESULTS

The myocardial mass of MCP perfusion territories (M_MCP) was related to the mass of reference standard perfusion territories (M_REF) by M_MCP = 0.99M_REF + 0.39 g (r = 1.00; R² = 1.00). The mass of AHA perfusion territories (M_AHA) was related to M_REF by M_AHA = 0.81M_REF + 5.03 g (r = 0.99; R² = 0.98).

CONCLUSION

The vessel-specific MCP myocardial perfusion territory assignment technique more accurately quantifies LCA and RCA perfusion territories as compared with the current standard AHA 17-segment model. Therefore, it can potentially provide a more comprehensive and patient-specific evaluation of coronary artery disease.

KEY POINTS

• The minimum cost path (MCP) technique accurately determines left and right coronary artery perfusion territories, as compared with the American Heart Association 17-segment (AHA) model. • The minimum cost path (MCP) technique could be applied to cardiac computed-tomography angiography images to accurately determine patient-specific left and right coronary artery perfusion territories. • The American Heart Association 17-segment (AHA) model often fails to accurately determine left and right coronary artery perfusion territories, especially in the inferior and inferoseptal walls of the left ventricular myocardium.

Low-Radiation-Dose Stress Myocardial Perfusion Measurement Using First-Pass Analysis Dynamic Computed Tomography: A Preliminary Investigation in a Swine Model

OBJECTIVES

The aim of this study was to assess the feasibility of a prospective first-pass analysis (FPA) dynamic computed tomography (CT) perfusion technique for accurate low-radiation-dose global stress perfusion measurement.

MATERIALS AND METHODS

The prospective FPA technique was evaluated in 10 swine (42 ± 12 kg) by direct comparison to a previously validated retrospective FPA technique. Of the 10 swine, 3 had intermediate stenoses with fractional flow reserve severities of 0.70 to 0.90. In each swine, contrast and saline were injected peripherally followed by dynamic volume scanning with a 320-slice CT scanner. Specifically, for the reference standard retrospective FPA technique, volume scans were acquired continuously at 100 kVp and 200 mA over 15 to 20 seconds, followed by systematic selection of only 2 volume scans for global perfusion measurement. For the prospective FPA technique, only 2 volume scans were acquired at 100 kVp and 50 mA for global perfusion measurement. All prospective global stress perfusion measurements were then compared with the corresponding reference standard retrospective global stress perfusion measurements through regression analysis. The CTDIvol and size-specific dose estimate of the prospective FPA technique were also determined.

RESULTS

All prospective global stress perfusion measurements (PPRO) at 50 mA were in good agreement with the reference standard retrospective global stress perfusion measurements (PREF) at 200 mA (PPRO = 1.07 PREF -0.09, r = 0.94; root-mean-square error = 0.30 mL/min per gram). The CTDIvol and size-specific dose estimate of the prospective FPA technique were 2.3 and 3.7 mGy, respectively.

CONCLUSIONS

Accurate low-radiation-dose global stress perfusion measurement is feasible using a prospective FPA dynamic CT perfusion technique.

Right ventricular oxygen delivery as a determinant of right ventricular functional reserve during exercise in juvenile swine with chronic pulmonary hypertension

Assessing right ventricular (RV) functional reserve is important for determining clinical status and prognosis in patients with pulmonary hypertension (PH). In this study, we aimed to establish RV oxygen (O₂) delivery as a determinant for RV functional reserve during exercise in swine with chronic PH. Chronic PH was induced by pulmonary vein banding (PVB), with sham operation serving as control. RV function and RV O₂ delivery were measured over time in chronically instrumented swine, up to 12 wk after PVB at rest and during exercise. At rest, RV afterload (pulmonary artery pressure and arterial elastance) and contractility (E_es and dP/dt_max) were higher in PH compared with control with preserved cardiac index and RV O₂ delivery. However, RV functional reserve, as measured by the exercise-induced relative change (Δ) in cardiac index, dP/dt_max, and end-systolic elastance (E_es), was decreased in PH, and RV pulmonary arterial coupling was lower both at rest and during exercise in PH. Furthermore, the increase in RV O₂ delivery was attenuated in PH during exercise principally due to a lower systolic coronary blood flow in combination with an attenuated increase in aorta pressure while arterial O₂ content was not significantly altered in PH. Moreover, RV O₂ delivery reserve correlated with RV functional reserve, Δcardiac index (r² = 0.85), ΔdP/dt_max (r² = 0.49), and ΔE_es (r² = 0.70), all P < 0.05. The inability to sufficiently increase RV O₂ supply to meet the increased O₂ demand during exercise is principally due to the reduced RV perfusion relative to healthy control values and likely contributes to impaired RV contractile function and thereby to the limited exercise capacity that is commonly observed in patients with PH.NEW & NOTEWORTHY Impaired right ventricular (RV) O₂ delivery reserve is associated with reduced RV functional reserve during exercise in a swine model of pulmonary hypertension (PH) induced by pulmonary vein banding. Our data suggest that RV function and exercise capacity might be improved by improving RV O₂ delivery.