768 JACC Vol 7, No .) AprIl 1986768-74

Diastolic Mitral Regurgitation in Patients With Atrioventricular Conduction Abnormalities: A Common Finding by Doppler

IOANNIS P. PANIDIS, MD, FACC, JOHN ROSS, RCPT, BRIAN MUNLEY, MD, PASQUALE NESTlCO, MD, GARY S. MINTZ, MD, FACC Philadelphia, Pennsylvania

M-mode and Doppler echocardiography were performed to depend on the position of the P wave in . With in 16 patients with first degree atrioventricular (A V) early diastolic P waves, the end of mitral valve flow by block, 1 patient with second degree (Wenckebach type) Doppier technique occurred 230 to 250 ms after the onset and 3 patierits with third degree AV block; 20 individuals of the P wave and was foliowed by mild diastolic mitral with a normal PR interval served as control subjects. regurgitation of variable dUration. With P waves falling The time from the onset of the P wave to the mitral valve in , the mitral valve remained open throughout closure by M-mode and to the end of mitral flow by diastole; during most of diastole, however, there was Doppler echocardiography were obtained. In 20 normal neither forward mitral flow (diastasis) nor diastolic rili• subjects, the P wave to mitral valve c10slire interval tral regurgitation detected by Doppler technique. For• measured 220 ± 30 ms by M-mode and to the end of ward aortic flow velocities by Doppler recording were mitral flow 225 ± 29 ms by Doppler technique (p = not different in cardiac cycles with or without diastolic NS). In patients with first degree AV block, these inter• mitral regurgitation. vals measured 242 ± 41 and 249 ± 36 ms, respectively It is concluded that prolongation of the PR interval (p == NS). can result in development of a left ventricular-left atrial Late diastolic (before the onset of the QRS complex) pressure gradient in diastole induced by the atrial con• mitral regurgitation was detected by pulsed mode Dbp• traction and premature mitral valve closure, which is pier imaging in 9 (56%) of the 16 patients with first probably incomplete and is often associated with dia• degree AV block but in none with a normal PR interval. stolic mitral regurgitation of no apparent hemodynamic In the four patients with advanced AV block, intermit• significance. tent mid or late diastolic mitral regurgitation was found (J Am Coli CardioI1986;7:768-74)

The mechanism of mitral valve closure has been the subject erly timed ventricular systole, the closure of the mitral valve 6f several experimeIltal and clinical studies (1-6) dating is incomplete and may be followed by a certain degree of back to 1843. However, continuing controversy exists re• presystolic mitral regurgitation (8-12). garding the precise pathophysiologic sequence and signifi• M-mode echocardiography has been used in the study of cance of the dynamic events involved in its closure (7). mitral valve motion during normal and in Nbrmal closure of the mitral valve is probably affected by various AV conduction abnormalities (6,8,13,14). The ad• a combination of atrial and ventricular contraction. Atrial vent of Doppler echocardiography provides the opportunity systole initiates a closing motion of the valve, which is then to accurately record and time the mitral valve flow patterns completed by ventricular systole in the presence of a normal and assess the presence and severity of mitral regurgitation atrioventricular (A V) sequencing (PR interval < 200 ms) (15,16). A combination of these two techniques was utilized (4,5). When the atrial contraction is not followed by a prop- in our study to examine the motion of the mitral valve and its flow characteristics in patients with normal sinus rhythm From the Likoff Cardiovascular Institute, Hahnemann University. Phil• and in those with various degrees of A V block. adelphia, Pennsylvania, Manuscnpt received September 24, 1985; revised manuscript received November 13. 1985, accepted November 26, 1985, Methods Address for reprints: Ioannis p, Panidis, MD, Cardiac Ultrasound Lab• oratory, Hahnemann University Hospital, 230 North Broad Street. MS313, Study patients. The study population included 20 sub• Philadelphia, Pennsylvania 19102-1192, jects (8 men, 12 women) with normal sinus rhythm (PR

© 1986 liy the AmerIcan College of Cardiology 0735-1097/86/$350 JACC Vol. 7, No 4 PANIDIS ET AL 769 Apnl 1986,768-74 DIASTOLIC MITRAL REGURGITATION IN AV CONDUCTION ABNORMALITIES

interval ~ 200 ms) (group I) and 16 patients (12 men, 4 I: women) with first degree A V block (PR interval> 200 ms) (group II). In addition, four other patients, aged 38 to 70 years, with advanced A V block (one with second degree, Wenckebach type, and three with complete block) were included, All these patients had technically adequate M-mode and Doppler echocardiograms. Of the 20 group I subjects (normal PR interval), 13 were normal by history, physical examination and echocardiography, 4 had mitral valve prolapse, 1 had congenital heart disease, I had coro• nary artery disease and I had cardiomyopathy. Of the 16 group II patients (prolonged PR interval), 4 had coronary artery disease, 6 had hypertension, 3 had cardiomyopathy ECG and 3 had mitral valve prolapse. Of the four patients with p p high degree AV block, one woman had hypertension and coronary artery disease and had a ventricular demand pace• maker inserted; the other three patients had no evidence of Figure 1. Pulsed mode Doppler recording in a patient with first cardiac disease by history, physical examination and echo• degree AV block (PR interval 320 ms). The sample volume is cardiographic evaluation, although one of them presented placed just below the mitral valve. Mitral regurgitation (MR) is with whereas the other two were asymptomatic and shown in systole (white arrowhead), A distinct signal is also seen in end-diastole (black arrowhead), which begins before the onset complete was an incidental finding. of the QRS complex (long arrow) and represents diastolic mitral Echocardiography. M-mode echocardiograms of the regurgitation. ECG = electrocardiogram, mitral valve were obtained with the IREX-II independent system and were recorded on a strip chart recorder at a paper speed of 50 or 100 mmls. Doppler studies were performed immediately after the M-mode study by the same technician of the QRS complex. The P wave to mitral valve closure using a phased array echocardiographic system (IREX-Me• interval (in milliseconds) was defined as the interval from ridian) with combined pulsed and continuous mode capa• the onset of the P wave to the coaptation of the anterior and bilities and a 2 MHz transducer. The sample size of the posterior leaflets at the end of closing motion of the mitral pulsed mode Doppler system is 7 x 7 mm and at a depth valve (C point) by M-mode echocardiogram. The onset of of 7 to 8 cm a peak velocity of 2.0 to 2.2 mls can be the P wave to the end of forward mitral flow interval by measured. The Doppler output signal was displayed in a Doppler echocardiography, which often coincided with a spectral format on a strip chart recorder and provided both clearly recorded closing spike, was also measured. The in• the direction and velocity of blood flow. A simultaneous terval (in milliseconds) from the onset of the QRS complex electrocardiogram was obtained during both the M-mode to mitral valve closure or the end of mitral flow was con• and Doppler echocardiographic studies with particularly sidered positive if the mitral valve closure or the end of careful recording of the P waves and onset of the QRS mitral flow occurred after the onset of the QRS complex complexes. and negative if it occurred before the onset of the QRS The apical four chamber view on two-dimensional echo• complex. cardiography was used for the detection of mitral regur• Statistical analysis. All measurements in the text are gitation. With the guidance of two-dimensional imaging, expressed as mean ± SD or range. Statistical comparison the sample volume of the pulsed mode Doppler echocar• between groups I and II was made by the unpaired t test diograph was placed inside the left just below the and between M-mode and Doppler echocardiographic mea• mitral valve leaflets. When a clear-cut spectral signal was surements by the paired t test. Correlation between the PR recorded below baseline at this site, mild mitral regurgitation interval and the onset of the QRS complex to the end of the was considered to be present (15,16). Mitral regurgitation mitral flow interval was performed with linear regression was then classified as systolic when the onset of the regur• analysis. A probability (p) value less than 0.05 was con• gitant jet was recorded after the peak of the R wave and sidered statistically significant. diastolic when the regurgitant jet began before the onset of the QRS complex on a simultaneously recorded electrocar• diogram (Fig. I). Results Measurements. The PR interval (in milliseconds) was Effect of the PR interval. The PR interval was 166 ± measured during both the M-mode and Doppler echocar• 30 ms (range 120 to 200) in group I and 264 ± 33 ms diographic studies from the onset of the P wave to the onset (range 220 to 330) in group II, There was no difference in 770 PANIDIS ET AL. lACC Vol 7, No 4 DIASTOLIC MITRAL REGURGITATION IN AV CONDUCTION ABNORMALITIES Apnl 1986 768-74

the PR interval as measured during the M-mode and Doppler after ventricular systole and not affecting the valve closure, study in 28 of the 36 patients and it differed by less than the mitral valve, after an initial closing motion, remained 10 ms in the remaining 8 patients. The P wave to end of open throughout diastole on M-mode recording to be finally mitral flow interval by Doppler study measured 225 ± 29 closed after an end-diastolic P wave. Doppler study at sim• ms (range 180 to 280) in group I and 249 ± 36 ms (range ilar RR and PR intervals revealed early forward mitral flow, 190 to 330) in group II patients (p = 0.04). These mea• then interruption of flow signals, although the mitral valve surements were somewhat less (220 ± 30 and 242 ± 41 remained open on M-mode study (diastasis). and a re• ms, respectively) by M-mode study (p = NS). The mitral sumption of flow after an end-diastolic P wave (Fig. 3). flow by Doppler study always ended after the onset of the With early or mid-diastolic P waves (PR interval 330 (0 :( QRS complex (onset of QRS to end of mitral flow 60 ± 1,000 ms), closure of the mitral valve on M-mode recordi~~ 16 ms [range 30 to 90]) in patients with a normal PR interval, and interruption of forward flow signals by Doppler study but often before the onset of the QRS complex in patients were usually observed 230 to 250 ms (mean 242 ± 6) after with first degree AV block (onset of QRS to end of mitral the onset of the preceding P wave and was followed by a flow - 15 ± 56 ms [range - 110 to 70]) (p < 0.00001), clearly defined mitral regurgitant jet during the rest of di• especially in those with a PR interval greater than 280 ms astole. The mitral valve during that period appeared closed (Fig. 2). on M-mode, and no forward transvalvular flow signals were Although systolic mitral regurgitation of mild degree was recorded in the Doppler study. This diastolic mitral regur• detected in 8 of the 20 patients with a normal PR interval, gitation was of mild degree, detected by pulsed mode Dop• none of them had evidence of diastolic mitral regurgitation pler echocardiography only just below the mitral valve into by Doppler study. In contrast, end-diastolic mitral regur• the left atrium and was not appreciated by auscultation. gitation was present in 9 (56%) of the 16 patients with first Three of the four patients with advanced A V block had degree A V block and was accompanied by systolic mitral no evidence of systolic mitral regurgitation by Doppler study. regurgitation in 7 of them. The two spectral signals of sys• In one patient with complete heart block and systolic mitral tolic and end-diastolic mitral regurgitation could often be regurgitation by Doppler study, clear separation of the two clearly separated (Fig. 1); visualization of isolated end-di• spectral signals of systolic and diastolic mitral regurgitation astolic mitral regurgitation was more difficult. Of the nine having different jet velocities was demonstrated during grad• patients with end-diastolic mitral regurgitation, seven had ual prolongation of the PR interval in successive cycles (Fig. a PR interval of 280 ms or more. 4). An excellent negative linear correlation (r = -0.99) Patients with advanced A V block. In patients with sec• between the PR interval and the onset of the QRS complex ond (one patient) or third degree (three patients) A V block, to the end of the mitral flow interval by Doppler recording a characteristic mitral valve motion by M-mode and mitral was observed in the three patients with complete heart block flow pattern by Doppler echocardiography were observed (Fig. 5). The interruption of forward mitral flow signals (Fig. 3). With P waves occurring during or immediately occurred before the onset of the QRS complex in cycles

(+) 100 oOlastolic MR -No MR 80 Figure 2. Correlation between the PR in- terval and the onset of QRS to end of 60 - - r=-.83 . - p= .0001 mitral valve (MY) flow interval as deter- 40 - • y =-.76x +185 mined by Doppler echocardiography in - patients with sinus rhythm. This interval is shorter in the 16 patients with a pro- 12>-2 20 0 _ u31 longed PR interval (> 200 ms) and in 9 ....o-g_ oE 0 PR Interval of them the end of mitral valve flow oc- ii~ (ms) curred before the onset of QRS as indi- co"" 20 0 cated by a negative ( - ) measurement; all o ... "- these 9 patients had evidence of diastolic 40 mitral regurgitation (MR) by Doppler study. None of the 20 subjects with a 60 0 normal PR interval had diastolic mitral 0 regurgitation. 80 0 0 100 (-) 0 JACC Vol 7, No 4 PANIDIS ET AL. 771 Apnl 1986:768-74 DIASTOLIC MITRAL REGURGITATION IN Av CONDUCTION ABNORMALITIES

Figure 3. M-mode echocardiogram (above) and pulsed Doppler recording (below) with the sample volume placed just below the mitral valve (MV) in a patient with complete AV block. Al• though the two studies were not ob• tained simultaneously, they demon, strate similar RR and PR intervals. In the first complex, the first P wave oc, ,0 saa. , •.'" curs in end-systole and does not affect .... .-.01.•• "r the motion of the mitral valve. After "''*.'''#''':,,--,~ an initial closing motion, the mitral valve remains open throughout dias• tole on M-mode recording, but no for• ward flow signal is recorded during p p p , that time by Doppler study (diastasis). , ,':" -" ., iCG" .. _... _~ .• _~'.'_'M_~' .... ~_--.,:,\.~. Flow resumes after the second (end• diastolic) P wave until the closure of the mitral valve. In the second com• plex. the third P wave occurs in early diastole and initiates closure ofthe mi• tral valve and interruption of its for• ward flow (long vertical arrows); al• though the mitral valve appears to be closed on M-mode recording, mitral ,• regurgitation (MR) is detected in the • 1 remainder of diastole by Doppler re• cording (arrowhead). In the third l' complex, the fourth P wave occurs even f later in diastole and again initiates early closure of the mitral valve and inter• DOPPLER ruption of its forward flow in end• p p diastole, followed by end-diastolic '"~-~---EtG . mitral regurgitation. ECG = electro• cardiogram; RVOT = right ventric• ular outflow tract.

with a PR interval greater than 250 ms; it was then followed a closing motion of the valve. This "atriogenic" closure, by diastolic mitral regurgitation, particularly when the PR however, may not be complete and the mitral valve may interval was greater than 320 ms. reopen if the atrial contraction is not followed by a subse• Despite the early closure and interruption of mitral flow quent, properly timed ventricular systole (4-6). In patients signals and the occurrence of diastolic mitral regurgitation with a prolonged PR interval, atrial systole induces a dia• in cycles with a prolonged PR interval, the forward aortic stolic reversal of mitral flow (8) and development of a ven• flow in the four patients with advanced heart block was not triculoatrial pressure gradient (5) resulting in premature mid affected and similar peak velocities were observed in all or late diastolic closure of the mitral valve. This early clo• cardiac cycles (Fig. 6). Left ventricular function as deter• sure is probably not effective and may be accompanied by mined by two-dimensional echocardiography was normal in a certain amount of diastolic mitral regurgitation as sug• three of the four patients; one patient demonstrated only gested by studies in animals (8-10) and humans (11,12) mild distal septal and apical hypokinesia. using an electromagnetic flow probe, indicator-dilution techniques or contrast ventriculography. The effect of a prolonged PR interval on mitral valve Discussion motion has been studied by M-mode echocardiography in Mechanisms of mitral valve closure. Early experi• patients with first degree or advanced A V block (6,8.13, 14). mental studies (1-3) suggested that the abrupt ending of Doppler echocardiography is a sensitive noninvasive method foward flow through an open mitral valve as it occurs at the for the detection of even mild degrees of mitral regurgitation end of atrial contraction can result in a zone of negative and it can be useful in the semiquantitation of its severity pressure in the area of the mitral cusps and the formation (15.16). We used a combination of M-mode and Doppler of vortex or eddy currents behind its leaflets. thus initiating echocardiography with simultaneous to 772 PANIDIS ET AL lACC Vul 7. No 4 DIASTOLIC MITRAL REGURGITATION IN AV CONDUCTION ABNORMALITIES Apnl 1986 768--74

t ~ r • MVCC> "~'I:MR

\. , ., 1 rh ! ! !,.p ! ,.4 ! .4 A R ~- /p /P .. P /p.4 p-' ECG

study the mitral valve motion and flow characteristics and Figure 4. Pulsed mode Doppler recording with the sample volume assess the occurrence and timing of mitral regurgitation in placed just below the mitral valve in a patient with complete A V patients with various A V conduction abnormalities. block. In the first complex, systolic mitral regurgitation (MR) is shown (black arrowheads). In the second complex, the PR in• Patients with first degree A V block. Diastolic mitral terval is prolonged and an end-diastolic regurgitant jet separate regurgitation in our study was defined as a clear-cut regur• from the systolic mitral regurgitation is seen representing diastolic gitant jet detected by pulsed mode Doppler study in the area mitral regurgitation. In the subsequent three complexes, further prolongation of the PR interval is associated with clearly separated signals of diastolic and systolic mitral regurgitation having dif• ferent jet velocities (black arrowheads). In these complexes, di• astolic mitral regurgitation commences immediately after mitral valve closure (MVC) and interruption of forward mitral valve flow. ECG = electrocardiogram.

Figure 5. A negative linear correlation between the PR interval just below the mitral valve in the left atrium and occurring and the onset of QRS complex to end of mitral valve (MV) flow interval as determined by Doppler echocardiography in a patient before the onset of the QRS complex (Fig. l). End-diastolic with complete AV block. With P waves occurring earlier in diastole mitral regurgitation was found in 9 (56%) of the 16 patients (prolonged PR interval), the end of mitral valve flow occurs before with first degree A V block, and 7 of them had a PR interval the onset of the QRS complex (indicated by a [-] value). With of 280 ms or greater (Fig. 2). In seven of these patients PR intervals over 330 ms, the end of mitral valve flow occurs with associated systolic mitral regurgitation, separation of more than 100 ms before the onset of QRS complex and is followed by diastolic mitral regurgitation (MR) as detected by pulsed mode the two Doppler spectral signals of diastolic and systolic Doppler recording. mitral regurgitation was often possible. The fact that the (+) majority of these patients also had systolic mitral regurgi• 100 tation (due to mitral valve prolapse, mitral anular calcifi•

0 PR Interval cation or papillary muscle dysfunction) suggests that a dis• (ms) turbance in the function of the mitral valve apparatus may 100 be necessary to observe end-diastolic mitral regurgitation 200 UJ> after the atrial contraction in patients with first degree A V a: ~ U' o 3: 300 block (12). _'50,,_e i i§ 400 Mitral leaflet motion on M-mode echocardiography ac• curately reflects transmitral flow (17). This observation is s.sii 500 supported by our findings of similar onset of P wave to 600 mitral valve closure intervals by M-mode and onset of P 700 wave to end of transmitral forward flow by Doppler echo• 800 cardiography. Mechanical left ventricular systole usually (-) r =-:99 '-' Diastolic MR begins 52 ms after the onset of the QRS complex (18). POO .0001 • No MR Y= -.99x+236 When the onset of left ventricular systole is defined by left JACC Vol. 7. No 4 PANIDIS ET AL. 773 Apnl 1986 768-74 DIASTOLIC MITRAL REGURGITATION IN AV CONDUCTION ABNORMALITIES

curring 230 to 250 ms after the onset of the P wave, and the valve may remain closed during the remainder of diastole (6,21). Additional factors other than atrial systole may also affect the occurrence and duration of this diastolic mitral valve closure. These factors include the accumulation of a sufficient intraventricular volume (the "locking" volume) that is required to sustain the diastolic closure of the valve (23) and other variables such as the condition of the myo• cardium, the level of autonomic nervous system input, the -1.311)/sec and the size of the heart (7). Diastolic mitral regurgitation during complete heart block has been shown in animal studies (9,10) and in humans (11) using an indicator-dilution technique. We observed diastolic Figure 6. Pulsed mode Doppler recording of forward aortic flow mitral regurgitation after the diastolic closure of mitral valve in a patient with complete A V block. Despite the random occur• rence of P waves in diastole in the three complexes, forward aortic by an early atrial contraction in the four patients with ad• flow velocities remain the same (at 1.3 m1s). ECG = vanced heart block studied by pulsed mode Doppler echo• electrocardiogram. cardiography (Fig. 3). This isolated diastolic mitral regur• gitation was present during PR intervals ranging between 330 and 1,100 ms (Fig. 5), but it was usually of mild degree and could not be detected by auscultation. In one patient ventricular pressure recordings, then the termination of the with complete heart block and coexistent systolic mitral final rapid posterior motion of the mitral valve on M-mode regurgitation, documentation of two separate spectral sig• echocardiography occurs 25 ± 10 ms later (19). Conse• nals of diastolic and systolic mitral regurgitation was ob• quently, mitral valve closure by M-mode or Doppler echo• tained by Doppler study during progressive prolongation of cardiography occurring less than 50 ms after the onset of the PR interval in successive cardiac cycles (Fig. 4). The the QRS complex can be assumed to take place in end• continuous mode Doppler technique was not routinely used diastole and not to be affected by ventricular systole. In five in our study because the jet of diastolic mitral regurgitation patients in our study who had first degree AV block, the was often difficult to record and not well defined by this end of forward mitral valve flow and subsequent mitral technique. The pulsed mode Doppler technique is more regurgitation by Doppler study occurred 40 ms or less after sensitive in detecting even mild mitral regurgitation of low the onset of the QRS complex (Fig. 2). An end-diastolic flow velocity and at a depth of 7 to 8 cm peak velocities component of mitral regurgitation can be considered to be up to 2.0 to 2.2 m/s can be measured. The peak velocities present in these patients. Similar to previous studies in an• of the diastolic mitral regurgitant jet were always less than imals (20,21) and humans (11) which found that atrial con• 2.0 mls whereas those of systolic mitral regurgitation usually traction followed by a properly timed ventricular systole exceeded 2 mls with development of aliasing (Fig. 1, 3 and results in efficient closure of the mitral valve with minimal 4). The difference in velocities is reflective of the left ven• or no mitral regurgitation, our study found no evidence of tricular-left atrial pressure gradient across the mitral valve, end-diastolic mitral regurgitation in patients with a normal which is much higher in systole than in diastole. These PR interval. findings further support previous observations that diastolic Patients with advanced AV block. The motion of the mitral valve closure induced by a preceding atrial systole natural or prosthetic mitral valve has been studied by M• in patients with advanced AV block is not effective and mode echocardiography in patients with complete heart block, complete and is associated with diastolic mitral reflux of with or without an artificial pacemaker (6,13,14,22). The variable duration depending on the PR interval. mitral valve motion patterns in these patients is mainly de• Clinical implications. The hemodynamic consequences termined by the position of the P wave and the resulting of the interruption of forward mitral flow in diastole and atrial contraction in the . When the P waves the development of diastolic mitral regurgitation (of mild occur during or immediately after the end of ventricular degree) in patients with AV block are not well known. systole, they do not affect the motion of the mitral valve, Williams et al. (9) suggested that there is an optimal PR which remains open throughout diastole. However, we found interval varying with heart rate beyond which no forward mitral flow signal by Doppler study during most and systolic pressure tend to decrease. We observed no of the diastolic period (diastasis), during which left atrial difference in the forward aortic flow peak velocity and flow and left ventricular pressures are probably equal (Fig. 3). velocity integrals by Doppler recording during several car• When the P waves occur in early or mid-diastole, they diac cycles with a variable PR interval in the four patients initiate a closing motion of the mitral valve, usually oc- with advanced AV block (Fig. 6). These Doppler aortic 774 PANIDIS ET AL lACC Vol 7, No 4 DIASTOLIC MITRAL REGURGITATION IN AV CONDUCTION ABNORMALITIES Apnl 1986768-74

flow velocity signals are directly proportional to the stroke 9. Williams JCP, Vandenberg RA, Sturm RE, Wood EH. Presystolic volume, A decrease in forward aortic flow velocity and atriogenic mitral reflux developed at abnormally long PR Intervals. Cardiovasc Res 1968;3:271-7. velocity integral of 9 to 25% was found in patients with a 10 Williams JCP, O'Donnovan TPB, Vandenberg RA, Sturm RE, Wood ventricular demand pacemaker as compared with those with EH. Atriogenic mitral valve reflux: diastolic mItral incompetence fol• "physiologic" pacing and normal A V sequencing (24-26), lowing isolated atrial systole. Clrc Res 1968;22:19-27. The discrepancy with our results may be related to the small II. Rutishauser W, Wirz P, Gander M, Luthy E. Atriogenic diastolic number of patients in our study, different heart rates and reflux in pallents with atrioventncular heart block. Circulation the fact that all four patients with advanced A V block in 1966;34:807-17. our study had either normal (three patients) or only slightly 12. Wong M. Diastolic mitral regurgitatIOn. Haemodynamic and angio• graphic correlation. Br Heart J 1969;31:468-73. impaired (one patient) left ventricular function, 13. Burggraf GW, Crmge E. The first heart sound in complete heart block: Conclusion. Our findings suggest that premature dia• phono-echocardiographic correlations. Circulation 1974;50: 17-24. stolic mitral valve closure induced by atrial systole occurs 14. Panidis IP, Morganroth J, David D, Chen CC, Kotler MN. Prosthetic in patients with A V conduction abnormalities, This "atri• mitral valve motion during cardIac dysrhythmias as determined by ogenic" closure of the mitral valve, however, is probably echocardiography. Am J Cardiol 1983;51:996-1004. incomplete and is associated with diastolic mitral regurgi• 15. Abbasi AS, Allen M, DeCristofaro D, Ungar I. Detection and esti• tation, usually of mild degree, as assessed by Doppler echo• mation of the degree of mitral regurgitation by range-gated pulsed Doppler echocardiography. Circulation 1980;61: 143-7 . cardiography. The presence of systolic mitral regurgitation 16 Panidis IP, Mintz GS, Ross J. Doppler ultrasound semi-quantitative in almost all of our patients with first degree A V block evaluation of mitral and tncuspld regurgitation (abstr). Clin Res suggests that dysfunction of the mitral valve apparatus may 1985;33:217A playa role in the development of these phenomena. How• 17. Laiken SL, Johnson AD, Bhargava V, Rigo P. Instantaneous trans• ever, diastolic mitral regurgitation was observed in patients mitral blood flow and anterior mitral leaflet motion in man. Circulation 1979;59:476-82. with advanced A V block in the absence of a defective mitral 18. Braunwald E, Fishman AP, Coumand A. Time relationship of dynamic valve or systolic mitral regurgitation. These effects of a events in the cardiac chambers, and aorta in man. prolonged PR interval appear to be of no hemodynamic Circ Res 1956;4:100-7. significance, at least in patients with preserved left ventric• 19. Pohost GM, Dinsmore RE, Rubenstein 11, et al. The echocardiogram ular function. of the anterior leaflet of the mitral valve: correlation with hemodynamic and cineroentgenographic studies in dogs. Circulation 1975;51 :88-97. 20. Tsakins AG, Gordon DA, Padiyar R, Frechette D. Relation of mitral References valve opening and closing to left atrial and ventricular pressure in the intact dog. Am J Physiol 1978;234:HI46-51. I. Baumgarten A, Ueber dem Mechanismus durch welchen die Venosen 21. Naito M, Dreifus LS, Mardelli n, et al. Echocardiographic features herzklappen geschlossen werden. Arch Anat Physiol (Leipzig) of atrioventricular and ventriculoatrial conduction. Am J Cardiol 1843;463-70. 1980;46:625-33. 2. 1ohnson FE. Two modes of closure of the heart valves. Heart 1912;4:69-82. 22. Panidis IP, Dreifus LS, Michelson EL. Hemodynamic effects of car• dIaC pacing. In: Dreifus LS, ed. Pacemaker Therapy. Philadelphia: 3. Bellhouse B1. Mechanism of closure of the mitral valve (abstrl. Clin FA Davis, 1983:1-11. Sci 1970;39:13P. 23. David D, Michelson EL, Naito M, Chen CC, Schaffenburg M, Dreifus 4. Dean AL 1r. The movement of the mitral cusps In relationship to the LS. Diastolic "locking" of the mitral valve: the importance of atrial cardiac cycle. Am 1 Physiol 1916;40:206-17. systole and intraventricular volume. Circulation 1983;67:640-5. 5. Little RC. Effect of atrial systole on ventricular pressure and closure 24. Labovitz AJ, Williams GA, Redd RM, Kennedy HL. Noninvasive of the AV valves. Am J Physio1 1951;166:289-95. assessment of pacemaker by Doppler echocardiog• 6. Zaky A, Steinmetz E, Feigenbaum H. Role of atrium in closure of raphy: importance of left atrial size. J Am Coli CardioI1985;6:196-200. mitral valve in man. Am J Physiol 1969;217:1652-9, 25. Stewart WJ, Dicola VC, Harthome JW, Gillam LD, Weyman AE. 7. Little RC. The mechanism of closure of the mitral valve: a continuing Doppler ultrasound measurement of in patients with controversy. Circulation 1979;59:615-8. physiologic pacemakers. Am J Cardiol 1984;54:308-12. 8. Laniado S, Yellin E, Kotler M, Levy L, Stadler 1, Terdiman R. A 26. Zugibe FT, Nanda NC, Barold SS, Akiyama T. Usefulness of Doppler study of the dynamic relations between the mitral valve echogram and echocardiography in cardiac pacing: assessment of mitral regurgita• phasic mItral flow. Circulation 1975;51:104-13. tion, peak aortic flow velocity and atrial capture. PACE 1983;6:1350-7.