Inappropriate Sinus Tachycardia (IST) is a rare type of cardiac arrhythmia, within the category of supraventricular tachycardia (SVT). IST may be caused by the sinus node itself having an abnormal structure or function, or it may be part of a problem called dysautonomia, a disturbance and/or failure of the autonomic nervous system. Research into the mechanism and etiology (cause) of Inappropriate Sinus Tachycardia is ongoing.
IST is viewed by most to be a benign condition in the long-term. Symptoms of IST however, may be distracting and warrant treatment. The heart is a strong muscle and typically can sustain the higher-than-normal heart rhythm, though monitoring the condition is generally recommended.[1]
The mechanism and primary etiology of Inappropriate Sinus Tachycardia has not been fully elucidated. An autoimmune mechanism has been suggested as several studies have detected autoantibodies that activate beta adrenoreceptors in a portion of patients.[2][3] The mechanism of the arrhythmia primarily involves the sinus node and peri-nodal tissue[4] and does not require the AV node for maintenance. Treatments in the form of pharmacological therapy or catheter ablation are available, although it is currently difficult to treat successfully.
Contents
- 1 Symptoms
- 2 Diagnosis
- 3 Treatment
- 4 See also
- 5 References
- 6 External links
- 7 Literature
Symptoms
Symptoms reported by patients vary in frequency and severity.
Symptoms associated with IST include:
- Frequent or sustained palpitations[1]
- Dyspnea (shortness of breath) and palpitations on exertion
- Pre-syncope (feeling as if about to faint)
- Fatigue (physical)
- Dizziness
- Exercise intolerance
- Occasional paresthesia and cramping
- Symptoms associated with autonomic nervous system disturbance, including GI disturbance
inappropriate v-tach
Diagnosis
No formal diagnostic criteria exist. A diagnosis of Inappropriate sinus tachycardia is primarily one of exclusion and the following may be observed:
- Exclusion of all other causes of sinus tachycardia
- Common forms of supraventricular tachycardia (SVT) must be excluded
- Normal P wave morphology
- A resting sinus tachycardia is usually (but not always) present
- Nocturnal dip in heart rate
- Inappropriate heart rate response on exertion
- Mean heart rate in 24hrs >95bpm
- Symptoms are documented to be due to tachycardia
- Hypotension is occasionally observed
- Syncope (fainting) is occasionally reported
Treatment
IST has been treated both pharmacologically and invasively, with varying degrees of success. IST, in and of itself, is not indicative of higher rates of mortality, and non-treatment is an option chosen by many. Exercise and physical conditioning is often the most effective treatment for IST.[5]
Some types of medication tried by cardiologists and other physicians include: beta blockers, selective sinus node If channel inhibitors (ivabradine),[6] calcium channel blockers and antiarrhythmic agents. Some SSRI drugs are also occasionally tried and also treatments more commonly used to treat postural orthostatic tachycardia syndrome such as fludrocortisone. This approach is very much "trial-and-error". Patients with IST are often intolerant to beta blockers. A new selective sinus node inhibitor ivabradine is also being used to treat IST.
Invasive treatments include forms of catheter ablation such as sinus node modification[7] (selective ablation of the sinus node), complete sinus node ablation (with associated implantation of a permanent artificial pacemaker) and AV node ablation in very resistant cases (creation of iatrogenic complete heart block, necessitating implantation of a permanent artificial pacemaker).
See also
- Supraventricular tachycardia
- Sinus tachycardia
- Postural orthostatic tachycardia syndrome
- Dysautonomia
References
- ^ http://www.ncbi.nlm.nih.gov/pubmed/23265330
- ^ Chiale, Pablo A.; Garro, Hugo A.; Schmidberg, Jorge; Sánchez, Rubén A.; Acunzo, Rafael S.; Lago, Manuel; Levy, Gabriela; Levin, Mariano (2006). "Inappropriate sinus tachycardia may be related to an immunologic disorder involving cardiac β andrenergic receptors". Heart Rhythm 3 (10): 1182–6. doi:10.1016/j.hrthm.2006.06.011. PMID 17018348.
- ^ Nattel, Stanley (2006). "Inappropriate sinus tachycardia and beta-receptor autoantibodies: A mechanistic breakthrough?". Heart Rhythm 3 (10): 1187–8. doi:10.1016/j.hrthm.2006.07.019. PMID 17018349.
- ^ Sato, Toshiaki; Mitamura, Hideo; Murata, Mitsushige; Shinagawa, Kaori; Miyoshi, Shunichiro; Kanki, Hideaki; Takatsuki, Seiji; Soejima, Kyoko; Miyazaki, Toshihisa (2000). "Electrophysiologic findings of a patient with inappropriate sinus tachycardia cured by selective radiofrequency catheter ablation". Journal of Electrocardiology 33 (4): 381–6. doi:10.1054/jelc.2000.9648. PMID 11099363.
- ^ http://www.ncbi.nlm.nih.gov/pubmed/23265330
- ^ Zellerhoff, Stephan; Hinterseer, Martin; Felix Krull, Bastian; Schulze-Bahr, Eric; Fabritz, Larissa; Breithardt, Günter; Kirchhof, Paulus; Kääb, Stefan (2010). "Ivabradine in patients with inappropriate sinus tachycardia". Naunyn-Schmiedeberg's Archives of Pharmacology 382 (5–6): 483–6. doi:10.1007/s00210-010-0565-y. PMID 20859616.
- ^ Lee, Randall J.; Kalman, Jonathan M.; Fitzpatrick, Adam P.; Epstein, Laurence M.; Fisher, Westby G.; Olgin, Jeffrey E.; Lesh, Michael D.; Scheinman, Melvin M. (1995). "Radiofrequency Catheter Modification of the Sinus Node for 'Inappropriate' Sinus Tachycardia". Circulation 92 (10): 2919–28. doi:10.1161/01.CIR.92.10.2919. PMID 7586260.
External links
- Dysautonomia International
- IST UK
- Inappropriate sinus tachycardia by Dr Richard N. Fogoros
- Arrhythmia Alliance
- Electrophysiology & Arrhythmia - Tachycardia
Literature
- Yusuf, Shamil; Camm, A. John (2005). "Deciphering the sinus tachycardias". Clinical Cardiology 28 (6): 267–76. doi:10.1002/clc.4960280603. PMID 16028460.
- Still, A; Raatikainen, P; Ylitalo, A; Kauma, H; Ikaheimo, M; Anterokesaniemi, Y; Huikuri, H (2005). "Prevalence, characteristics and natural course of inappropriate sinus tachycardia". Europace 7 (2): 104–12. doi:10.1016/j.eupc.2004.12.007. PMID 15763524.
- Leon, Hernando; Guzman, Juan Camilo; Kuusela, TOM; Dillenburg, Rejane; Kamath, Mark; Morillo, Carlos A. (2005). "Impaired Baroreflex Gain in Patients with Inappropriate Sinus Tachycardia". Journal of Cardiovascular Electrophysiology 16 (1): 64–8. doi:10.1046/j.1540-8167.2005.04441.x. PMID 15673390.
- Sanchez-Quintana, D; Cabrera, JA; Farré, J; Climent, V; Anderson, RH; Ho, SY (2005). "Sinus node revisited in the era of electroanatomical mapping and catheter ablation". Heart 91 (2): 189–94. doi:10.1136/hrt.2003.031542. PMC 1768731. PMID 15657230.
- Cruz Filho, Fernando E. S.; Maia, Ivan G.; Fagundes, Marcio L. A.; Boghossian, Silvia; Ribeiro, José Carlos (1998). "Modificação do nódulo sinusal via cateter por energia de radiofreqüência em paciente com taquicardia sinusal inapropriada. Avaliação dos resultados imediatos e tardios" [Sinus node modification by catheter using radiofrequency current in a patient with inappropriate sinus tachycardia. Evaluation of early and late results]. Arquivos Brasileiros de Cardiologia (in Portuguese) 70 (3): 173–6. doi:10.1590/S0066-782X1998000300006. PMID 9674178.
- Lee, SH; Cheng, JJ; Kuan, P; Hung, CR (1997). "Radiofrequency catheter modification of sinus node for inappropriate sinus tachycardia: A case report". Zhonghua Yi Xue Za Zhi 60 (2): 117–23. PMID 9360339.
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