Atrial and ventricular programmed electrical stimulation in patients with symptomatic hypertrophic cardiomyopathy1 William A. Schiavone, D.O Hypertrophic cardiomyopathy is associated with a high inci- Harry M. Lever, M.D. dence of sudden death. Eight patients with symptomatic hyper- James D. Malpney, M.D. trophic cardiomyopathy were studied by atrial and ventricular programmed electrical stimulation in order to correlate the results with symptoms; with arrhythmias documented by continuous 24- hour electrocardiographic monitoring; and with electrocardi- ographic; echocardiographic, and hemodynamic measurements. Atrial stimulation induced sustained atrial tachyarrhythmias in 4 of 6 patients not having sustained atrial fibrillation prior to the study. Only 2 of these 6 patients had sustained atrial tachyarrhyth- mias documented by continuous 24-hour electrocardiographic monitoring; Ventricular stimulation induced sustained ventricular flutter-fibrillation in 1 of 8 patients—the patient with the longest run of unslistained ventricular tachycardia prior to our study. Atrial stimulation better identified patients who could sustain atrial tachyarrhythmias than continuous 24-hour electrocardi- ographic monitoring and demonstrated the hemodynamic consé- quences. Ventricular stimulation identified the patient most vul- nerable to sustained ventricular tachyarrhythmias. Results of atrial and ventricular programmed electrical stimulation may guide patient-management decisions in an attempt to reduce sud- den death due to hypertrophic cardiomyopathy. Index terms: Cardiac pacing, artificial • Electric stimulation • Idiopathic hypertrophic subvalvular stenosis Cleve Clin Q 51:601-609, Winter 1984 1 Department of Cardiology, The Cleveland Clinic Foundation. Submitted for publication Aug 1984; accepted C>ct 1984. sb Hypertrophic cardiomyopathy, a disease of unknown etiology, is characterized by nonspecific symptoms, includ- 0009-8787/84/04/0601/09/$3.25/0 ing exertional dyspnea, angina pectoris, lightheadedness, Copyright © 1984, The Cleveland Clinic and syncope. It is associated with a high incidence of Foundation sudden death.1,2 The best clinical predictors for sudden 601 Downloaded from www.ccjm.org on September 24, 2021. For personal use only. All other uses require permission. 602 Cleveland Clinic Quarterly Vol. 51, No. 4 Table 1. Historical data Patient No. Age Sex Family history Symptoms 1 24 M Brother (patient 4) with hypertrophic cardiomyopa- Palpitations, lightheadedness thy 2 51 M Brother died suddenly (cardiac death) at a young age Lightheadedness, worsening dyspnea on exertion, syn- cope (three times) 3 53 M Twenty-one-year-old son died of hypertrophic cardi- Lightheadedness, angina omyopathy 4 28 M Brother (patient 1) with hypertrophic cadiomyopathy Syncope while driving 5 73 F None Syncope (three times), worsening dyspnea on exertion 6 56 M None Worsening dyspnea on exertion, episodic lightheaded- ness 7 58 F None Syncope, dyspnea on exertion, palpitations 8 64 F None Lightheadedness, palpitatjons, pulmonary edema death are youth, strong family history of sudden thy and correlate the response with clinical symp- death, and progression of symptoms.3,4 Various toms, arrhythmias documented by 24-hour ECG, reports have suggested dynamic outflow obstruc- hemodynamic and anatomic data obtained by tion,5 decreased ventricular diastolic compliance two-dimensional and M-mode echocardiography, with inflow obstruction,2'6,7 and cardiac and left heart catheterization. arrhythmias8,9 alone or in concert to be the un- derlying causes of symptoms and vulnerability to Methods and materials sudden death. From May 1982 through January 1983, 85 We describe our initial experience with atrial patients with hypertrophic cardiomyopathy were and ventricular programmed electrical stimula- seen in the Department of Cardiology at the tion in patients with hypertrophic cardiomyopa- Cleveland Clinic. Only those with progressive Table 2. Initial ECG data Patient Rate P width PR interval QRS duration No. (beats/min) Rhythm (sec) (sec) P axis (sec) QRS axis 53 Sinus 0.14 0.18 -20° 0.11 + 175° 65 Sinus 0.12 0.16 +30° 0.10 +30° 75 Atrial fibrillation 0.10 -30° 68 Sinus 0.12 0.18 +30° 0.11 -75° 53 Sinus 0.14 0.21 + 120° 0.15 LBBB -30° 76 Sinus 0.12 0.19 +50° 0.08 +30° 72 Atrial fibrillation, 0.11 -60° VVI pacer 75 Sinus 0.15 0.24 +75° 0.08 0° Downloaded from www.ccjm.org on September 24, 2021. For personal use only. All other uses require permission. Winter 1984 Electrical Stimulation and hypertrophic cardiomyopathy 603 Table 3. Initial 24-hour ECG data Patient Medications Atrial arrhythmias Ventricular arrthythmias 1 Verapamil (160 q.i.d.) PACs Single VPBs 2 Verapamil (120 q.i.d.) Paroxysmal sustained SVT Trebeled VPBs 3 Propranolol (40 q.i.d.) Sustained atrial fibrillation Paired VPBs 4 Verapamil (80 t.i.d.) None Single VPBs Nadolol (80 q.d.) 5 Verapamil (120 t.i.d.) Paroxysmal sustained atrial fibrillation Single VPBs 6 None None Six-beat unsustained VT 7 Propranolol (20 q.i.d.) Sustained atrial fibrillation Single VPBs, VVI pacer Quinidine (200 q.i.d.) 8 Verapamil (120 t.i.d.) None Five-beat unsustained VT symptoms or a recent history of syncope were Technique of atrial stimulation included in our study. The high right atrium was stimulated with A careful history was obtained and a physical atrial premature impulses at progressively examination was performed. All patients under- shorter coupling intervals until atrial capture was went standard 12-lead and 24-hour ECG and M- lost. The high right atrium was next paced at a mode and two-dimensional echocardiography, as 600-msec cycle length, and a single premature well as left heart catheterization via the Sones extra stimulus was induced at progressively technique. Pressure measurements from the left shorter coupling intervals until loss of capture. ventricular apex, left ventricular outfldw tract, In the absence of an inducible sustained atrial and ascending aorta were taken in sequence at arrhythmia, the atrium was ramp-paced down to rest and after provocation with isoproterenol (2 200-msec cycle length. Induced atrial fibrillation to 8 jug, administered intravenously) or nitro- and atrial flutter were treated in a fashion best glycerin (0.4 mg, administered sublingually). All suited to the patient's hemodynamic status dur- patients underwent selective Coronary arteriog- ing the arrhythmia either by rapid atrial pacing, raphy and left cinè Ventriculography (right ante- by observing spontaneous conversion to sinus rior oblique and left anterior oblique projection). rhythm, or by direct-current cardioversion. Electrophysiologic studies Technique of ventricular stimulation We performed electrophysiologic studies for The right ventricular apex was paced at 600 all patients after sedating the patients with diaze- msec (SI-SI). Premature stimuli (S2) were initi- pam. Right atrial and right ventricular pro- grammed electrical stimulation was conducted in all patients with the use bf two or three multipolar catheters positioned in thè high right atrium and Table 4. Tachyarrhythmias right ventricular apex or in the high right atrium, Supraventricular right ventricular apex, and at the low right Paroxysmal atrium-His bundlé area. Intracardiac electro- Unsustairted (5-30 sec in duration) grams and surface electrocardiograms were si- Sustained (>30 sec in duration) Chronic (present throughout observation period) multaneously recorded via the Gould electro- static recorder. Programmed electrical stimula- Ventricular tion was performed with a Medtronic 5325 stim- Paroxysmal ulator with 1.8-msec rectangular pulses at twice Unsustained (5-20 beats with spontaneous termination) diastolic threshold. Sustained (>20 beats or requiring intervention) Downloaded from www.ccjm.org on September 24, 2021. For personal use only. All other uses require permission. 604 Cleveland Clinic Quarterly Vol. 51, No. 4 Table 5. Echocardiography data Patient Left atrium Septal thickness Resting No. Medications (mm) (mm) SAM 1 Verapamil (160 q.i.d.) 53 32 + 2 Verapamil (120 t.i.d.) 46 20 + 3 Propranolol (40 q.i.d.) 47 22 + Quinidine S04 (300 q.i.d.) 4 None 44 24 - 5 Verapamil (120 t.i.d.) 50 25 + 6 None 44 20 + 7 Propranolol (20 q.i.d.) 51 20 - Quinidine SO., (200 q.i.d.) 8 None 42 30 + SAM = systolic anterior motion of mitral valve. ated after every eighth paced beat, starting in twice this S1-S2 interval. The S3 was moved late diastole and repeating at progressively short- earlier in diastole at 20-msec decrements until it er coupling intervals until induction of a sus- failed to capture. Next, S2 was moved closer to tained ventricular tachyarrhythmia or loss of ven- SI by 10-msec decrements until both S2 and S3 tricular capture. When a sustained ventricular captured. This protocol was followed until either tachyarrhythmia could not be induced, a second induction of a sustained ventricular tachyarrhyth- extra stimulus (S3) was added. From the point of mia or failure of Capture of S2 occurred. If loss of capture of S2, S2 was moved outside the premature stimuli S2 and S3 failed to induce a effective refractory period, and S3 was added at sustained ventricular tachyarrhythmia, rapid ven- Tàble 6. Left heart catheterization data LVOT gradient (mm Hg) Patient No, Medications CAD MR Resting Provoked 1 Verapamil (160 q.i.d.) - - 25 45 I 2 Verapamil (120 t.i.d.) - - 30 120 I 3 Propranolol (40 q.i.d.) - - 30 1201 Quinidine S04 (300 q.i.d.) 4 None +25% right coronary artery - 0 70 I 5 Verapamil (120 t.i.d.) - Severe 80 100 N 6 None +30% right coronary