Handbook of Experimental Pharmacology - Part 1 pps

The components of the electrocardio- gram, and of extracellular electrograms directly recorded from the heart, could only be well understood by comparing such registrations with recordin

Basis and Treatment

of Cardiac Arrhythmias

Contributors

M.E Anderson, C Antzelevitch, J.R Balser, P Bennett,

M Cerrone, C.E Clancy, I.S Cohen, J.M Fish, I.W Glaaser, T.J Hund, M.J Janse, C January, R.S Kass, J Kurokawa,

J Lederer, S.O Marx, A.J Moss, S Nattel, C Napolitano,

S Priori, G Robertson, R.B Robinson, D.M Roden,

M.R Rosen, Y Rudy, A Shiroshita-Takeshita, K Sipido,

Y Tsuji, P.C Viswanathan, X.H.T Wehrens, S Zicha

Editors

Robert S Kass and Colleen E Clancy

123

Department of Physiology and Biophysics

Institute for Computational Biomedicine

Weill Medical College of Cornell University

ISBN-10 3-540-24967-2 Springer Berlin Heidelberg New York

ISBN-13 978-3-540-24967-2 Springer Berlin Heidelberg New York

Library of Congress Control Number: 2005925472

This work is subject to copyright All rights reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broad- casting, reproduction on microfilm or in any other way, and storage in data banks Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law

of September 9, 1965, in its current version, and permission for use must always be obtained from Springer Violations are liable for prosecution under the German Copyright Law.

Springer is a part of Springer Science + Business Media

Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book In every individual case the user must check such information by consulting the relevant literature.

Editor: S Rallison

Editorial Assistant: S Dathe

Cover design: design&production GmbH, Heidelberg, Germany

Typesetting and production: LE-TEX Jelonek, Schmidt & Vöckler GbR, Leipzig, Germany

Printed on acid-free paper 27/3151-YL - 5 4 3 2 1 0

In the past decade, major progress has been made in understanding nisms of arrhythmias This progress stems from much-improved experimen-tal, genetic, and computational techniques that have helped to clarify the roles

mecha-of specific proteins in the cardiac cycle, including ion channels, pumps, changer, adaptor proteins, cell-surface receptors, and contractile proteins Theinteractions of these components, and their individual potential as therapeu-tic targets, have also been studied in detail, via an array of new imaging andsophisticated experimental modalities The past 10 years have also led to therealization that genetics plays a predominant role in the development of lethalarrhythmias

ex-Many of the topics discussed in this text reflect very recently undertakenresearch directions including the genetics of arrhythmias, cell signaling mole-cules as potential therapeutic targets, and trafficking to the membrane Thesenew approaches and implementations of anti-arrhythmic therapy derive frommany decades of research as outlined in the first chapter by the distinguishedprofessors Michael Rosen (Columbia University) and Michiel Janse (University

of Amsterdam) The text covers changes in approaches to arrhythmia therapyover time, in multiple cardiac regions, and over many scales, from gene toprotein to cell to tissue to organ

New York, May 2005 Colleen E Clancy and Robert S Kass

List of Contents

History of Arrhythmias 1

M.J Janse, M.R Rosen

Pacemaker Current and Automatic Rhythms:

Toward a Molecular Understanding 41

I.S Cohen, R.B Robinson

Proarrhythmia 73

D.M Roden, M.E Anderson

Cardiac Na+ Channels as Therapeutic Targets

for Antiarrhythmic Agents 99

I.W Glaaser, C.E Clancy

Structural Determinants of Potassium Channel Blockade

and Drug-Induced Arrhythmias 123

X.H.T Wehrens

Sodium Calcium Exchange as a Targetfor Antiarrhythmic Therapy 159

K.R Sipido, A Varro, D Eisner

A Role for Calcium/Calmodulin-Dependent Protein Kinase II

in Cardiac Disease and Arrhythmia 201

T.J Hund, Y Rudy

AKAPs as Antiarrhythmic Targets? 221

S.O Marx, J Kurokawa

β-Blockers as Antiarrhythmic Agents 235

S Zicha, Y Tsuji, A Shiroshita-Takeshita, S Nattel

Experimental Therapy of Genetic Arrhythmias:

Disease-Specific Pharmacology 267

S.G Priori, C Napolitano, M Cerrone

Mutation-Specific Pharmacology of the Long QT Syndrome 287

R.S Kass, A.J Moss

VIII List of Contents

Therapy for the Brugada Syndrome 305

Tsuji, Y 235Varro, A 159Viswanathan, P.C 331Wehrens, X.H.T 123Zicha, S 235

2 M J Janse · M.R Rosen fibrillation, atrioventricular nodal re-entry and atrioventricular re-entrant tachycardia in hearts with an accessory atrioventricular connection The components of the electrocardio- gram, and of extracellular electrograms directly recorded from the heart, could only be well understood by comparing such registrations with recordings of transmembrane potentials The first intracellular potentials were recorded with microelectrodes in 1949 by Coraboeuf and Weidmann It is remarkable that the interpretation of extracellular electrograms was still controversial in the 1950s, and it was not until 1962 that Dower showed that the trans- membrane action potential upstroke coincided with the steep negative deflection in the electrogram For many decades, mapping of the spread of activation during an arrhythmia was performed with a “roving” electrode that was subsequently placed on different sites

on the cardiac surface with a simultaneous recording of another signal as time reference This method could only provide reliable information if the arrhythmia was strictly regular When multiplexing systems became available in the late 1970s, and optical mapping in the 1980s, simultaneous registrations could be made from many sites The analysis of atrial and ventricular fibrillation then became much more precise The old question whether an arrhythmia is due to a focal or a re-entrant mechanism could be answered, and for atrial fibrillation, for instance, the answer is that both mechanisms may be operative The road from understanding the mechanism of an arrhythmia to its successful therapy has been long: the studies of Mines in 1913 and 1914, microelectrode studies in animal prepara- tions in the 1960s and 1970s, experimental and clinical demonstrations of initiation and termination of tachycardias by premature stimuli in the 1960s and 1970s, successful surgery

in the 1980s, the development of external and implantable defibrillators in the 1960s and 1980s, and finally catheter ablation at the end of the previous century, with success rates that approach 99% for supraventricular tachycardias.

Keywords Electrocardiogram · Extracellular electrograms · Transmembrane potentials ·

Re-entry · Focal activity · Tachycardias · Fibrillation

a more rational basis for diagnosing many arrhythmias Still, the conceptthat disturbances in the electrical activity of the heart were responsible forabnormal arterial and venous pulsations was not universally known at the turn

of the nineteenth century For example, MacKenzie observed that the A wavedisappeared from the venous curve during irregular heart action, and wrote, in

History of Arrhythmias 3

1902 under the heading of “The pulse in auricular paralysis”, “I have no clearidea of how the stimulus to contraction arises, and so cannot definitely say howthe auricle modifies the ventricular rhythm But as a matter of observation Ican with confidence state that the heart has a very great tendency to irregularaction when the auricles lose their power of contraction.”

The first demonstration of the electrical activity of the heart was madeaccidentally by Köllicker and Müller in 1856 Following the experiments ofMatteuci in 1842, who used the muscle of one nerve-muscle preparation as

a stimulus for the nerve of another, thereby causing its muscle to contract(see Snellen 1984), they also studied a nerve-muscle preparation from a frog(sciatic nerve and gastrocnemius muscle) Accidentally, the sciatic nerve wasplaced in contact with the exposed heart of another frog, and they observedthe gastrocnemius muscle contract in synchrony with the heartbeat They sawimmediately before the onset of systole a contraction of the gastrocnemius,and in some preparations a second contraction at the beginning of diastole.Although Marey (1876) first used Lipmann’s capillary electrometer to recordthe electrical activity of the frog’s heart, the explanation for this activity wasprovided by the classic experiments of Burdon-Sanderson and Page (1879,1883) They also used the capillary electrometer together with photographicequipment to obtain recordings of the electrical activity of frog and tortoisehearts They placed electrodes on the basal and apical regions of the frog heartand observed two waves of opposite sign during each contraction The timeinterval between the two deflections was in the order of 1.5 s By injuring thetissue under one of the recording sites, they obtained the first monophasicaction potentials and showed how, in contrast to nerve and skeletal muscle,there is in the heart a long period between excitation and repolarization [“

if either of the leading-off contacts is injured the initial phase is followed

by an electrical condition in which the injured surface is more positive, orless negative relatively to the uninjured surface: this condition lasts duringthe whole of the isoelectric period ” (Burdon-Sanderson and Page 1879)]

A second important observation was that by partially warming the surface “ the initial phase (i.e of the electrogram) is unaltered but the terminal phasebegins earlier and is strengthened” (Burdon-Sanderson and Page 1879).Heidenhain introduced the term arrhythmia as the designation for any dis-turbance of cardiac rhythm in 1872 With the introduction of better techniques

to record the electrical activity of the heart, the study of arrhythmias developed

in an explosive way We will limit this brief account to those studies in whichthe electrical activity was documented, even though we will make an exceptionfor a number of seminal papers on the mechanisms of arrhythmias in whichneither mechanical nor electrical activity was recorded (McWilliam 1887a,b,1889; Garrey 1914; Mines 1913b, 1914) We will pay particular attention tothe early studies, nowadays not easily accessible, and will not attempt to give

a complete review of all arrhythmias

of sulphuric acid in a narrow glass capillary Whenever a potential differencebetween the mercury and the acid is applied, changed or removed, this bound-ary moves (see Snellen 1995) The capillary electrometer was sensitive, butslow Einthoven constructed his string galvanometer, which was both sensitiveand rapid, based on the principle that a thin, short wire of silver-coated quartzplaced in a narrow space between the poles of a strong electromagnet will movewhenever the magnetic field changes as a consequence of change in the currentflowing through the coils During the construction of the string galvanometer,Einthoven was aware of the fact that Ader in 1897 also had used an instrumentwith a string in a magnetic field as a receiver of Morse signals transmitted

by undersea telegraph cables In Einthoven’s first publication on the stringgalvanometer, he did quote Ader (Einthoven 1901) It is often suggested thatEinthoven merely improved Ader’s instrument However, as argued by Snellen(1984, 1995), Ader’s instrument was never used as a galvanometer, i.e as aninstrument for measuring electrical currents, and if it had, its sensitivity wouldhave been 1:100,000 that of the string galvanometer To quote Snellen (1995):

“ the principle of a conducting wire in a magnetic field moving when a rent passes through it, had been known from Faraday’s time if not earlier, that

cur-is three quarters of a century before Ader Equalizing all possible instrumentswhich use that principle is perhaps just as meaningless as to put a primitivehorse cart on a par with a Rolls Royce, because they both ride on wheels.”Figure 1 shows electrocardiograms recorded with the capillary electrometer

by Waller and by Einthoven, Einthoven’s mathematical correction of his tracing,and the first human electrocardiogram recorded by Einthoven with his stringgalvanometer (Einthoven 1902, 1903)

Remarkably, Einthoven constructed a cable which connected his ical laboratory with the Leiden University hospital, over a distance of a mile(Einthoven 1906) This should have created a unique opportunity to collabo-rate with clinicians and document the electrocardiographic manifestations of

physiolog-a host of physiolog-arrhythmiphysiolog-as Unfortunphysiolog-ately, physiolog-according to Snellen (1984):

Occurrence of extrasystoles had the peculiar effect that Einthoven couldwarn the physician by telephone that he was going to feel an intermission

of the pulse at the next moment It seems that this annoyed the clinicianwho was poorly co-operative anyway; in fact, after only a few years hecut the connection to the physiological laboratory This must have been

History of Arrhythmias 5

Fig 1 Panel 1: Waller’s recording of the human electrocardiogram using the capillary

elec-trometer t, time; h, external pulsation of the heart; e, electrocardiogram Panel 2: Einthoven’s tracing published in 1902 also with the capillary electrometer, with the peaks called A, B, C, and D In the lower tracing, Einthoven corrected the tracing mathematically, and now used the terminology P, Q, R, S and T Panel 3: One of the first electrocardiograms recorded with

the string galvanometer as published in 1902 and 1903 by Einthoven (Reproduced from Snellen 1995)

a blow to Einthoven, although in 1906 and 1908 he had already collectedtwo impressive series of clinical tracings Precisely at this time, a youngphysician and physiologist from London approached him who needed

to improve his registration method of the relation between auricularand ventricular contraction in what ultimately proved to be auricularfibrillation This was Thomas Lewis

There is no doubt that Lewis was foremost in introducing Einthoven’s ment into clinical practice and in experiments designed to unravel mechanisms

instru-of arrhythmias (see later) Einthoven always appreciated Lewis’s work When

6 M J Janse · M.R Rosen

Einthoven received the Nobel prize in 1925, he said in his acceptance speech:

“It is my conviction that the general interest in electrocardiography wouldnot have risen so high, nowadays, if we had to do without his work and Idoubt whether without his valuable contribution I would have the privilege

of standing before you today” (Snellen 1995) Others who quickly employedEinthoven’s instrument were the Russian physiologist Samojloff, who in 1909published the first book on electrocardiography, and Kraus and Nicolai whopublished the second book in 1910 (see Krikler 1987a,b)

Initially, only the three (bipolar) extremity leads were used Important velopments were the introduction of the central terminal and the unipolarprecordial leads by Wilson and associates (Wilson et al 1933a), and of aug-mented extremity leads by Goldberger (1942) Wilson and Johnston (1938) alsopaved the way for the development of vectorcardiography

de-The first body-surface maps, based on 10 to 20 electrocardiograms recordedfrom the surface of a human body were published by Waller in 1889 However,the distribution of isopotential lines on the human body surface at differentinstants of the cardiac cycle took off after the publication by Nahum et al.(1951)

Ambulatory electrocardiography began with Holter’s publication in 1957.Further developments in electrocardiography include body surface His bundleelectrocardiography, computer analysis of the electrocardiogram, the signal-averaged electrocardiogram, polarcardiography and the magnetocardiogram.For a detailed description of these techniques, the reader is referred to the book

Comprehensive Electrocardiology, edited by MacFarlane and Lawrie (1989).

A large number of books on the electrocardiography of arrhythmias hasbeen published, and here we will only refer to a few, all written by one or twoauthors (Samojloff 1909; Kraus and Nicolai 1910; Lewis 1920, 1925; Lepeschkin1951; Katz and Pick 1956; Spang 1957; Scherf and Cohen 1964; Scherf and Schott1973; Schamroth 1973; Pick and Langendorf 1973; Josephson and Wellens1984), and ignore the even greater number of multi-authored books

2.2

The Interpretation of Extracellular Waveforms

Pruitt (1976) gives a very interesting account of the controversy, confusionand misunderstanding about the interpretation of extracellular electrograms

in the 1920s and 1930s In those days, one generally used the terminology

of Lewis (1911), who had written that “the excited point becomes negativerelative to all other points of the musculature and the wave of negativitytravels in all directions from the point of excitation.” Burdon-Sanderson andPage (1879) had in fact already written, “Every excited part of the surface of the

ventricle is during the excitatory state negative to every unexcited part” (their

italics) Others interpreted these ideas in the sense that the spread of activation

History of Arrhythmias 7

was equal to the propagation of a “wave of negativity” Although Lewis clearly

indicated that the excited part of the heart was negative relative to the unexcited

parts, he never used the terms doublet or dipole Craib (see Pruitt 1976) was thefirst to “formulate a concept of myocardial excitation that entailed movementalong the fibre not of a wave of negativity, but of an electrical doublet”, thelatter defined as “intimately related and closely lying foci or loci of raisedand lowered potentials” Wilson and associates (1933b) introduced the termbipole, which, much the same as Craib’s doublet, represented “two sources ofequal but opposite potential lying close together” The word source here may beconfusing since Wilson also introduced the terms source and sink, meaning thepaired positive and negative charges associated with propagation of the cardiacimpulse In retrospect, the controversy that led to the estrangement of Lewisand Craib (Pruitt 1976) is difficult to understand and seems largely semantic.Why should cardiologists quarrel about the question whether “negativity”could exist on its own, without “positivity” in the immediate neighbourhood?

In addition to the misunderstanding concerning propagation of a wave of

“negativity”, there is confusion in the early literature regarding the question

of which deflection in the extracellular electrogram reflects local excitation.Some of the difficulties in interpreting electrograms directly recorded fromthe surface of the heart seem to be related to the fact that in the early daysonly bipolar recordings were used It took a long time before the concept that

a bipolar recording is best understood as the sum of two unipolar recordingsbecame widely accepted among cardiac electrophysiologists (Strictly speak-ing, there is of course no such thing as a unipolar recording We use the termunipolar to indicate that one electrode is positioned directly on the heart, theother electrode, the “indifferent” one, far away In bipolar recordings, both ter-minals are close together on the heart’s surface.) Lewis introduced the terms

“intrinsic” and “extrinsic” deflections, and although we still use these termstoday, we do not mean precisely the same thing Lewis (1915) wrote: “(1) Thereare deflections which result from arrival of the excitation process immediatelybeneath the contacts; these we term intrinsic deflections (2) There are alsodeflections which are yielded by the excitation wave, travelling in distant areas

of the muscle To these we apply the term extrinsic deflections.” He proves hispoint by recording a bipolar complex from the atrium The “usual tall spike”

is preceded by a small downward deflection Crushing the tissue under theelectrode pair results in disappearance of the tall spike (the intrinsic deflec-tion), but the small initial deflection (the extrinsic deflection) remains (Lewis1915) Lewis called this a fundamental observation, and he was right Still, for

us the terminology is somewhat confusing Today we use bipolar recordings toget rid of extrinsic deflections The reasoning is that each terminal is affected

to (almost) the same degree by extrinsic potentials (far field effects), whichare therefore cancelled when one electrode terminal is connected to the neg-ative pole of the amplifier, the other terminal to the positive pole What thenremains is not one single intrinsic deflection, but two intrinsic deflections,

a single large rapid negative deflection, the intrinsic deflection.

Although Wilson and associates (1933b) introduced unipolar and lar recordings, the precise interpretation of the various components of suchrecordings was not completely clear even in the 1950s Durrer and van derTweel began recording unipolar and bipolar electrograms from intramural,multipolar needle electrodes inserted in the left ventricular wall of goats anddogs in the early 1950s In 1954 they wrote: “In all cases where a fast part

bipo-of the intrinsic deflection (i.e in unipolar recordings, MJJ and MRR) could

Fig 2 Unipolar (UP) and bipolar (diff ECG) electrograms recorded from the epicardial

surface of a canine heart The direction of the excitation wave and the position of the three

electrodes are indicated in the lower panel Bipolar complexes recorded from electrodes 1 and 2 and from electrodes 2 and 3 are shown, together with a unipolar complex from electrode 2 The intrinsic deflection in the unipolar recording coincides with the intersection

of the descending limb from bipolar complex 1–2 and with the ascending limb of bipolar complex 2–3 Recordings made by Durrer and van der Tweel circa 1960

History of Arrhythmias 9

be detected, the top of the differential spike (i.e the bipolar recording) wasfound to coincide with it” (Durrer and van der Tweel 1954a) In other words,the “intrinsic deflection” in bipolar electrograms was thought to be the top ofthe spike In a subsequent paper (Durrer et al 1954b), they found that “thewidth of the bipolar complex increased proportionally to the distance betweenthe intramural lead points” The implication here is that the bipolar complexhas two intrinsic deflections Figure 2 is an unpublished recording by Durrerand van der Tweel that must have been made in 1960, since a very similarfigure was published in 1961 (Durrer et al 1961) Here it can be seen thatthe intrinsic deflection in the unipolar recording from terminal 2 coincideswith the intersection of the descending limb of the bipolar complex recordedfrom terminals 1 and 2, and the ascending limb from the bipolar signal fromterminals 2 and 3

That the steep, negative-going downstroke in the unipolar extracellular trogram coincides with the upstroke of the transmembrane action potential

elec-Fig 3 Microelectrode recordings from the epicardial surface of an in situ canine heart In the

upper panel, both microelectrodes A and B are in the extracellular space as close together as

possible, the reference electrode is somewhere in the mediastinum Note that the “bipolar”

electrogram A–B is almost a straight line In the lower panel, microelectrode A is lar, microelectrode B extracellular Note contamination of the unipolar recording of A with extrinsic potentials, and how A–B gives the true transmembrane potential (Reproduced

intracellu-from Janse 1993)