Using Human Hearts to Study...

Using Human Hearts to

Study Arrhythmogenesis

Igor R. Efimov, Ph.D., F.A.I.M.B.E., F.A.H.A., F.H.R.S.The Alisann and Terry Collins Professor & Chairman, Department of Biomedical

EngineeringNational Academies of Science, Engineering, Medicine: Public Workshop on the Uses of Dogs in Biomedical Research

National Academies Keck Center Building. 500 5th St. NW Washington, DC 20001 March 27-28, 2019

Present on the state of the science for using human hearts in cardiovascular

disease research.

What accomplishments/advancements have been made in the recent past (last 5

– 10 years) in cardiovascular disease through the use of human hearts in

research?

Could any of these accomplishments/advancements have been achieved in

other species?

From your perspective, what is the likelihood of in vitro models replacing dogs as

the preferred model for cardiovascular disease going forward?

What would be the tradeoffs in doing so?

Would replacing dogs with another species compromise the quality or timelines

of future advances?

Present on the state of the science for using human hearts in

cardiovascular disease research.

What accomplishments/advancements have been made in the recent past (last 5

– 10 years) in cardiovascular disease through the use of human hearts in

research?

Could any of these accomplishments/advancements have been achieved in

other species?

From your perspective, what is the likelihood of in vitro models replacing dogs as

the preferred model for cardiovascular disease going forward?

What would be the tradeoffs in doing so?

Would replacing dogs with another species compromise the quality or timelines

of future advances?

Jeanne M. Nerbonne, and Robert S. Kass Physiol Rev 2005;85:1205-1253

Jeff Robbins (Circ. Res., 2011): “What have we learned in the past

20 years? Although the pace of data acquisition and subsequent

definition of multiple signaling pathways, gene function, and normal

and pathogenic mechanisms has been exhilarating, we cannot help

but be humbled by the relatively tiny impact of these data on human

health in general and cardiovascular disease specifically. Our “wet

bench” advances have not, with rare exceptions, been translated to

the bedside. Although this failure is due at least in part to our inability

to effectively apply what we have learned to drug development, it

also reflects remaining, serious deficits in understanding the

mechanisms that drive cell and organ function.”

Present on the state of the science for using human hearts in cardiovascular

disease research.

What accomplishments/advancements have been made in the recent past

(last 5 – 10 years) in cardiovascular disease through the use of human hearts

in research?

Could any of these accomplishments/advancements have been achieved in

other species?

From your perspective, what is the likelihood of in vitro models replacing dogs as

the preferred model for cardiovascular disease going forward?

What would be the tradeoffs in doing so?

Would replacing dogs with another species compromise the quality or timelines

of future advances?

Basic electrophysiology: SA and AV

nodes

Pathophysiology: arrhythmia mechanisms

Human heart disease OMICS

Human heart No. 136. The two-year old child heart. v=musculature of the atrial septum; k=node; m=anterior mitral leaflet;

s=the atrioventricular fibrous septum; t=septal leaflet of the tricaspid valve; h=initial portion of the ventricular bundle; r &

l= the right and the left bundle brunches of the conduciton system; sf=a tendinous fiber of the septal leaflet of the

tricuspid valve; km=musculature of the ventricular septum.

Tawara S, Das Reizleitungssystem Des Saugetierherzens, Gustav Fischer, Jena, 1906

Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J

Anat Physiol 1907; 41:172–189.

Lewis T, Meakins J, White PD. The Excitatory Process in the Dog's Heart. Part I. The Auricles. Philosophical

Transactions of the Royal Society of London. Series B, Vol. 205, (1914), pp. 375-420

Boineau et al., Am J Physiol, 1988

37

SAN cells Atrial cells Connective

tissue

Coronary

arteries

Fedorov, Circ Res, 2009

Fedorov, JACC 2010

Fedorov, JACC 2010

Boineau et al., Am J Physiol, 1988Fedorov, JACC 2010

Fedorov, JACC 2010

Kistler et al. P-Wave Morphology in Focal Atrial Tachycardia. J Am Coll Cardiol 2006;48:1010 –7.

Mendez C, Moe GK. Circ Res. 1966;19:378–393

Hucker, An. Rec. 2007

Hucker, An. Rec. 2007

Fedorov, Circ: EA, 2011

Fedorov, Circ: EA, 2011

Basic electrophysiology: SA and AV nodes

Pathophysiology: arrhythmia mechanisms

Human heart disease OMICS

George R. Mines, On Dynamic Equilibrium of the Heart. J. Physiol., 1913, XLVI, 349-383

Wavelength λ = Refractory Period x Conduction velocity

Reentry is possible only if wavelength < pathlength (1D)

George R. Mines (1886-1914)

Figure 1. a: Spiral wave using the TNNP human ventricular cell model (bottom panel) and the Luo-Rudy phase 1 model

for gs (conductance of the slow inward current) = 0 (top panel). The medium size is 25 × 25 cm and 5 × 5 cm. The

effective size of both patterns is L = 2.5. b: The relative effective size of the heart S vs heart mass. Here S = I /Ihuman, where

I is evaluated from Equation 1, and Ihuman is I for the human heart.

Panfilov AV, Is heart size a factor in ventricular fibrillation? Or how close are rabbit and human hearts? Heart Rhythm,

2006, 3(7):862-4.

Effective size (L) of the tissue: L = D/λ, D - the size of the tissue; λ - the wavelength.

Laughner, AJP 2012 Gloschat, Sci Rep 2018

Lou, AJP 2012

Qing Lou

Lou, AJP 2012

Qing Lou

Lou, AJP 2012

• Wavelength = conduction velocity x action potential duration (refractory period) • WSA (Wavelength surface area) = longitudinal wavelength * transverse wavelengths• Arrhythmia can be sustained only is WSA < Ventricular surface area:

• WSA(BDM) = 19-34 cm2

• WSA(Blebbistatin) = 39-60 cm2

• Ventricular epicardial surface area = 39.4+/-1.8 cm2

Qing Lou

Lou, AJP 2012

Kedar Aras

Aras, Circ: A&E, 2018

Kedar Aras

Aras, Circ: A&E, 2018

Kedar Aras

Wavelength volume: Vλ= λLongitudinal x λTransverse x λTransmural

Aras, Circ: A&E, 2018

Kedar Aras

Wavelength volume: Vλ= λLongitudinal x λTransverse x λTransmural

Aras, Circ: A&E, 2018

Kedar Aras

Endo

L-trans

R-trans

Epi

Aras, Circ: A&E, 2018

1 - Early (‘organized’) VF versus disorganized VF is

associated with different characteristics of drivers

2- VF mainly driven by reentrant activity (~88% wavefronts)

3- Focal breakthroughs- dominant origin from RV

Superimposed 252 egms in VF

****

Haissaguerre et al, Localized Structural Alterations Underlying a Subset of Unexplained Sudden Cardiac Death, Circ: A&E, 11(7), e006120

Haissaguerre et al, Localized Structural Alterations Underlying a Subset of Unexplained Sudden Cardiac Death, Circ: A&E, 11(7), e006120

Small animal models are necessary to develop the

experimental tools and scientific vocabulary to conduct

research of the mechanisms of ventricular fibrillation

Human heart research is needed to determine human

specific mechanisms of VT/VF

Basic electrophysiology: SA and AV nodes

Pathophysiology: arrhythmia mechanisms

Human heart disease OMICS

Matkovich et al, Widespread Downregulation of Cardiac Mitochondrial and Sarcomeric Genes in Patients with Sepsis. Crit. Care Med. 2016.

Matkovich et al, Widespread Downregulation of Cardiac Mitochondrial and Sarcomeric Genes in Patients with Sepsis. Crit. Care Med. 2016.

Matkovich et al, Widespread Downregulation of Cardiac Mitochondrial and Sarcomeric Genes in Patients with Sepsis. Crit. Care Med. 2016.

Hemerich et al., Integrative Functional Annotation of 52 Genetic Loci Influencing Myocardial Mass Identifies Candidate Regulatory Variants and Target

Genes. Circ Genom Precis Med. 2019 Feb; 12(2):e002328.

Hemerich et al., Integrative Functional Annotation of 52 Genetic Loci Influencing Myocardial Mass Identifies Candidate Regulatory Variants and Target

Genes. Circ Genom Precis Med. 2019 Feb; 12(2):e002328.

Hemerich et al., Integrative Functional Annotation of 52 Genetic Loci Influencing Myocardial Mass Identifies Candidate Regulatory Variants and Target

Genes. Circ Genom Precis Med. 2019 Feb; 12(2):e002328.

Novel promoters in FANTOM5

51

Promoter-level heart transcriptome

for ventricular remodeling studies

52

Promoter-level heart transcriptome

for ventricular remodeling studies

Deviatiiarov, unpublished 201953

Deviatiiarov, unpublished 2019

55

Overlapped regulatory features – 333 in our data vs 244 from Ensembl

6% upstream SNPsSNP

20%

SNPs in heart-CAGE

promoters

Ensemblpromoters 204940

FANTOM5enhancers 65420

GWAS(heart SNPs 5104)

pro/enhHeart CAGE: 1050/33

Ensembl: 431/17

Disease-associated

mutations:

Present on the state of the science for using human hearts in cardiovascular

disease research.

What accomplishments/advancements have been made in the recent past (last 5

– 10 years) in cardiovascular disease through the use of human hearts in

research?

Could any of these accomplishments/advancements have been achieved in

other species?

From your perspective, what is the likelihood of in vitro models replacing

dogs as the preferred model for cardiovascular disease going forward?

What would be the tradeoffs in doing so?

Would replacing dogs with another species compromise the quality or

timelines of future advances?

The canine model is the closest to human in terms of normal

and pathological electrophysiology.

Translational therapy development for chronic atrial and

ventricular arrhythmias requires large animal models prior to

human trials, with the canine model preferable.

Human heart is the best model for Omics studies due to genetic

differences.

A national program is needed to utilize widely available for

research donor human hearts which are rejected for

transplantation, and not used.

Acknowledgments:

- Oleg Gusev, Riken Institute, Yokohama, Japen

- Washington Regional Transplant Community, Mid-America Transplant Services

- US National Heart, Lung, and Blood Institute, NIH, R01HL114395, R01HL085369, R01HL141470,

R21EB023106…

- Leducq Foundation Transatlantic Network of Excellence RHYTHM.