The only stupid question is one that isn't asked
I'm going to start by asking you a question, before I get into the explanation of my condition and symptoms

. Do you have symptoms which concern you, and if so what are they? It is possible for heart disorders to go undetected because symptoms are not present, or are mistaken for other disorders, but you also said that you had an echo. That would catch a lot of potential problems. In the absence of any other symptoms or reason to believe that you might have a problem, that's probably all that you need. In answer to your question you would definately know if you had the symptoms I am going to describe and I think the same is true of most conditions. If the symptoms were there, you'd know that something wasn't 'right' and hopefully get it checked out

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I have an atrial septal defect (ASD) which means there is a tiny hole between the two upper chambers of my heart (the atrium - your heart has four chambers; two atrials & two ventricles). In my case it is a congenital defect - which means the hole was present when I was born. This causes a heart murmur (a sound that the heart makes from the blood going back and forth through the hole, that can be heard with a stethescope). It also causes oxygenated and unoxygenated blood to get mixed which, depending on the size and severity of the hole can either cause no problems or very serious problems.
When I was younger it caused significant problems. I would become short of breath and sometimes faint when exerting myself, and my heart had to work harder to get enough oxygenated blood to my body. This made me tire easily and have irregular heart rythms. These irregular rythms caused atrial and ventricular tachycardia, two episodes of ventricular fibrillation that required emergency services and in one instance my heart actually stopped.
Fortunately as I grew the hole grew smaller as tissue naturally began to close over it, though it did not close all the way (I am 24 now). The main symptoms that I have now are palpitations or "skipped beats." The technical names are Premature Atrial Contractions (PACs) and Premature Ventricular Contractions (PVCs). What happens is after a normal heartbeat, the heart tries to beat again too soon and the heart's electrical system hasn't had a chance to reset itself properly. This causes a slightly longer pause before the next full beat, which tends to feel "harder" because there is then more blood to be pumped through the heart. It feels like the heart missed a beat, but it actually had an extra one

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Sometimes several of these premature beats will come in a row with no normal beats in between. This usually last from three to five seconds and my heart-rate is slightly elevated after an episode of that nature. Episodes lasting longer than a few seconds usually cause dizziness or even fainting (though that hasn't happened in a while thankfully).
The number of premature beats I get in any given day varies. Sometimes I won't notice any all day, and other days I will get two or three a minute for hours at a time. I'm in reasonably good physical condition but if I do too much streneous exercise then I tend to tire and/or get out of breath before similarly fit peers. Ironically it is after exercise that I tend to get more premature beats, not during.
My heart-rate also tends to be quite low when I wake in the morning if I wake on my own without being awakened by an alarm clock or telephone ringing. Also when exercising I can stay within my "target heart rate zone" but when I stop, even if I do a thorough cool-down, my heart-rate drops dramatically (to slightly lower than my normal resting rate), and then gets back into my normal resting heartrate range after a few minutes. I think it is this sudden change that causes the increased symptoms after exercise.
After a recent round of routine tests to check on the condition of my heart, since I do have the ASD, I was informed of options for treatment that didn't exist or were in the early and risky stages when I was a young child. If the ASD begins to cause significant problems (it can sometimes lead to cardiomyopathy - enlargement of the heart due to the overworked muscle, or irregular rhythms which could be dangerous - PVCs and PACs generally are not a danger in and of themselves), a surgical proceedure can be performed to patch the hole with a peice of specially designed mesh that facilitates tissue growth and causes the hole to close completely.
Currently the only treatment I am on is a daily multivitamin, the herb hawthorn berry, and a potassium supplement (under the advice of my doctor). I also have to have the doctor call in a prescription for antibiotics any time I am going to have dental work or anything of that nature which could lead to bacteria entering the bloodstream, and of course I have to be careful to avoid being exposed to streptococus (sp?) bacteria (strep throat) and get to the doctor for antibiotics if I am. This is because I am at an increased risk for pericarditis - an infection or inflamation of the lining of the heart muscle.
Anyway sorry to write a novel. I hope this helps to answer your questions and if you want to know anything more about my condition feel free to ask

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