Abnormal Vascular, Metabolic, and Neural Function During Exercise in Heart Failure With Preserved Ejection Fraction

Protocol 1.1: To test hypothesis 1.1 the investigators will measure rapid onset vasodilation
in response to a single KE contraction as a marker of vascular responsiveness to muscle
contraction, as well as the dynamic onset, and steady state vasodilatory responses to
continuous KE exercise. The rapid onset vasodilatory (ROV) response to a brief (1-second)
single isometric knee extension contraction will be measured as described by our
collaborators50. Subjects will perform single contractions at 5, 10 or 20% of their maximal
voluntary contraction (MVC). Beat-by-beat local vascular responses (i.e. femoral blood flow;
FBF and vascular conductance; FVC) will be recorded continuously for 30-seconds with the
initial response (first un-interrupted cardiac cycle post-contraction), peak response
(maximal increase), latency (time to peak response) and area under the curve (total
vasodilator response across 30-seconds) analyzed to fully characterize ROV in HFpEF.
Additionally, the vascular and hemodynamic response to dynamic KE exercise (beat-by-beat
onset and steady state FBF and FVC) will be measured from the onset of exercise for six
minutes at submaximal work rates (10, 15 W, and 60% maximal work rate). These trials will be
performed individually and with 20 minutes of rest between conditions to ensure that patients
will be able to complete each of these trials. In addition to local vascular hemodynamics,
systemic hemodynamics (HR, MAP, CO, SV) will be monitored throughout to confirm that any
alterations in local blood flow are independent of central cardiovascular adjustments (See
Fig. 2, Day 2)

Hypothesis 1.2: Skeletal muscle V̇O2 kinetics will be slowed in HFpEF.

Protocol 1.2: Breath-by-breath pulmonary V̇O2 kinetics will be measured during cycle exercise
at a relatively light work rate of 20 W (~30% V̇O2 peak) to characterize V̇O2 kinetics where
there is no cardiac limitation, allowing for a submaximal assessment of "peripheral"
oxidative efficiency during large muscle mass exercise. During cycle exercise, V̇O2 kinetics
will be measured in conjunction near infrared spectroscopy as a marker of the coupling
between oxygen delivery and demand (see Fig. 2, Day 3).

Hypothesis 1.3: HFpEF patients will demonstrate elevated MSNA at rest, and exaggerated
metaboreflex sensitivity during exercise.

Protocol 1.3: Microneurography will be used to measure multi-unit muscle sympathetic nerve
discharge in subjects at rest, during dynamic knee extension exercise (30, 40% MVC), and
during 2 minutes and 15 seconds of post-exercise ischemia (PEI) achieved via inflation of a
blood pressure cuff to supra-systolic pressure. This approach allows for experimental
isolation of the metaboreflex contribution to changes in MSNA and hemodynamics by preventing
washout of metabolites produced by muscle contraction during exercise. Importantly, the
sympathetic response is independent of the confounding activation of the mechanoreflex or
central command as muscle contractions are no longer being performed. A cold pressor test
will be utilized to confirm specific sensitivity to the metaboreflex and not generalized
sensitivity to sympathoexcitatory stimuli. Multi-unit post-ganglionic MSNA will be recorded
from the peroneal nerve using standard microneurographic techniques and quantified as burst
frequency (bursts/min), burst incidence (burst/100 cardiac cycles) and total activity (burst
frequency x mean burst amplitude).

Experimental Series 2 - Global Hypothesis 2: isolating peripheral adaptations to exercise
training using single KE exercise training will improve peripheral vascular, metabolic, and
neural function and result in greater functional capacity in HFpEF.

Approach: Hypothesis 2.1: Isolated KE exercise training will improve the vasodilatory
response to exercise, speed V̇O2 kinetics, and reduce MSNA at rest HFpEF.

Protocol 2.1: 1) Vascular response: ROV will be assessed as described in protocol 1. Subjects
will perform single contractions at 5, 10 or 20% of their pre- and post-testing maximal
voluntary contraction (MVC). The peripheral hemodynamic response to dynamic KE exercise
(beat-by-beat onset and steady state) will be measured continuously from the onset of
exercise for six minutes at the same absolute (10, and 15 W) and relative (60% of
post-intervention maximal work rate) exercise intensities. Local vascular (FBF, FVC) and
systemic (HR, MAP, CO, SV) hemodynamics will be monitored throughout these trials to confirm
that any alterations in local blood flow are independent of central cardiovascular
adaptations (See Fig 2, Day 2). 2) V̇O2 Kinetics: Breath-by-breath Pulmonary V̇O2 kinetics
will be measured during isolated single KE exercise and during upright cycle exercise.
Dynamic KE exercise will be performed for six minutes at the same absolute submaximal work
rates (10 and 15 W) as well as the same relative (60% post-intervention maximal work rate;
see Fig 2, Day 2) in conjunction with beat-by-beat blood flow measures. Additionally, V̇O2
kinetics will be assessed during mild intensity cycle exercise at 20 W and utilized as a
marker of intervention efficacy as discussed above (see Fig. 2, Day 3). 3) MSNA:
Microneurography will be used to measure multi-unit muscle sympathetic nerve discharge in
subjects at rest, during knee extension exercise, and PEI (See Fig 2, Day 3).

Hypothesis 2.2: Single KE exercise training will improve whole body exercise tolerance, peak
V̇O2, and functional capacity in HFpEF.

Protocol 2.2: In addition to submaximal V̇O2 kinetics: maximal KE work rate, peak V̇O2 during
cycle exercise, and performance in the 6-minute walk test will be re-evaluated after isolated
quadriceps exercise training in the same manner as prior to the intervention (see specific
exercise training protocol below).

All subjects will be >65 years of age. The controls will be screened carefully for
hypertension and cardiac disease, including structural heart and hemodynamically
significant obstructive coronary disease, using a history, physical examination, and
resting and post-exercise transthoracic echocardiograms. Additional exclusion criteria for
this group will include valvular heart disease, atrial flutter/ fibrillation, renal
insufficiency, chronic lung disease, regular cigarette smoking within the past 10 years,
and cardiovascular medication. Subjects demonstrating greater than moderate levels of
activity > 2 days per week will not be allowed to participate, as chronic high levels of
physical activity could potentially impact the primary outcome variables.

- HFpEF Inclusion Criteria:

- Patients will be > 65 years old

- We will use a modification of the European Guidelines for the diagnosis of HFpEF to
select the patient population.

- The key components of these guidelines include:

- signs and symptoms of heart failure;

- b) an ejection fraction > 0.50; and

- c) objective evidence of diastolic dysfunction. To satisfy the first criteria, we
will use the Framingham criteria (dyspnea, orthopnea, PND, edema); however we
will require objective evidence of congestion including

- chest X-ray,

- elevated BNP,

- or elevated PCWP (pulmonary capillary wedge pressure) or

- LVEDP (left ventricular end-diastolic pressure) > 16 mmHg; for the second, we will
accept echo, nuclear or catheter documentation; and for

- we will require a depressed tissue Doppler mitral annular velocity < 7.5 cm/s along
with PCWP > 16 mmHg if available.

HFpEF Exclusion Criteria:

- underlying valvular or congenital heart disease;

- restrictive or infiltrative cardiomyopathy;

- acute myocarditis;

- NYHA Class IV CHF, or CHF that cannot be stabilized on medical therapy;

- other condition that would limit the patient's ability to complete the protocol;

- manifest ischemic heart disease.

- Patients with CABG or previous history of atrial fibrillation will be allowed to
participate, though for safety reasons, patients on Coumadin will be excluded.

- All patients must be in sinus rhythm without a left bundle branch block at the time of
study, and be off beta blockers or non-dihydropyridine Ca++ blockers for at least 5
half-lives. β blockers will be weaned over 3-5 days and additional doses of
vasodilators added to control blood pressure if necessary. Drugs that affect the
renin-angiotensin-aldosterone system and diuretics will be maintained.